home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
InfoMagic Standards 1994 January
/
InfoMagic Standards - January 1994.iso
/
ccitt
/
1988
/
troff
/
3_2_01.tro
< prev
next >
Wrap
Text File
|
1991-12-12
|
140KB
|
4,724 lines
.rs
.\" Troff code generated by TPS Convert from ITU Original Files
.\" Not Copyright ( c) 1991
.\"
.\" Assumes tbl, eqn, MS macros, and lots of luck.
.TA 1c 2c 3c 4c 5c 6c 7c 8c
.ds CH
.ds CF
.EQ
delim @@
.EN
.nr LL 40.5P
.nr ll 40.5P
.nr HM 3P
.nr FM 6P
.nr PO 4P
.nr PD 9p
.po 4P
.rs
\v | 5i'
.sp 1P
.ce 1000
\v'12P'
\s12PART\ I
\v'4P'
.RT
.ce 0
.sp 1P
.ce 1000
\fBRecommendations G.211 to G.544\fR \v'2P'
.EF '% \ \ \ ^''
.OF ''' \ \ \ ^ %'
.ce 0
.sp 1P
.ce 1000
\fBLINE\ TRANSMISSION\fR \v'2P'
.ce 0
.sp 1P
.ce 1000
INTERNATIONAL\ ANALOGUE\ CARRIER\ SYSTEMS
.ce 0
.sp 1P
.LP
.rs
.sp 26P
.LP
.bp
.LP
.rs
.sp 10P
.LP
\fBMONTAGE:\ \fR PAGE 2 = PAGE BLANCHE
.sp 1P
.RT
.LP
.bp
.sp 1P
.ce 1000
\v'3P'
SECTION\ 2
.ce 0
.sp 1P
.ce 1000
\fBGENERAL\ CHARACTERISTICS\ COMMON\ TO\ ALL\fR
.ce 0
.sp 1P
.ce 1000
\fBANALOGUE\ CARRIER\(hyTRANSMISSION\ SYSTEMS\fR
.ce 0
.sp 1P
.IP
\fB2.1\ Definitions and general considerations\fR
.sp 1P
.RT
.sp 2P
.LP
\fBRecommendation\ G.211\fR
.RT
.sp 2P
.ce 1000
\fBMAKE\(hyUP\ OF\ A\ CARRIER\ LINK\fR
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.211''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.211 %'
.ce 0
.sp 1P
.ce 1000
\fI(amended at Geneva, 1964; further amended)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.PP
In the international telephone network, provision must be made for the
interconnection of various sorts of carrier\(hytransmission systems
using symmetric cable pairs, open\(hywire lines, coaxial cable pairs or
radio\(hyrelay links. It is thus desirable for the carrier equipment used in
these various systems, and which is not confined to a particular sort of
line, to meet general CCITT recommendations.
.sp 1P
.RT
.PP
Basically, these equipments comprise translating equipments and
through\(hyconnection filters.
.sp 2P
.LP
\fB1\fR \fBTranslating equipments\fR
.sp 1P
.RT
.PP
These equipments are classified below according to the procedure
used to make up the large\(hycapacity systems from the basic supergroup.
.PP
Two procedures are in use:
.PP
\fIProcedure\ 1:\fR \ the mastergroup and supermastergroup procedure;
.PP
\fIProcedure\ 2:\fR \ the 15\(hysupergroup assembly procedure; their use is
described in the Recommendations concerning the various line systems.
.PP
For international links, procedure\ 2 can be used above 4\ MHz only by
agreement between the Administrations concerned, including the agreement
of
the Administration(s) of the transit country or countries, if any.
.PP
In the Recommendations, the names of the equipments defined above are also
used for equipments which translate a basic group, supergroup or
mastergroup or a basic (No.\ 1) 15\(hysupergroup assembly into the line\(hyfrequency
band and vice versa.
.PP
The translating equipments used in procedure\ 1 are:
.RT
.LP
\(em
channel\(hytranslating equipment, for translating the
audio\(hyfrequency band into the basic group and vice versa
(see Recommendations\ G.232, G.234\ [1] and\ G.235);
.LP
\(em
group\(hytranslating equipment for translating five basic groups
into the basic supergroup and vice versa;
.LP
\(em
supergroup\(hytranslating equipment for translating five basic
supergroups into the basic mastergroup and vice versa;
.LP
\(em
mastergroup\(hytranslating equipment for translating three basic
mastergroups into the basic supermastergroup and vice versa;
.LP
\(em
supermastergroup\(hytranslating equipment for translating the
basic supermastergroup into the line\(hyfrequency band and
vice versa.
.PP
\fINote\fR \ \(em\ Figure\ 1/G.211, \fIa)\fR and \fIb)\fR recapitulates
the basic
frequency bands used in procedure\ 1; the through\(hyconnection possibilities
described in Recommendation\ G.242 are provided for in these
bands.
.bp
.LP
.rs
.sp 42P
.ad r
\fBFigure 1/G.211, p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
The translating equipments used in procedure\ 2 are:
.LP
\(em
channel\(hytranslating equipment and group\(hytranslating
equipment, as defined for procedure\ 1;
.LP
\(em
supergroup\(hytranslating equipment for translating 15\ basic
supergroups into the basic assembly\ No.\ 1 of 15\ basic
supergroups and vice versa;
.LP
\(em
15\(hysupergroup assembly equipment for translating basic
assembly\ No.\ 1 of 15\ supergroups into the frequency
band of the 15\(hysupergroup assembly\ No.\ 3 and vice versa;
.LP
\(em
supermastergroup\(hytranslating equipment for translating
15\(hysupergroup assembly\ No.\ 3 into the line\(hyfrequency band
and vice versa.
.bp
.PP
\fINote\ 1\fR \ \(em\ Figure\ 1/G.211, \fIa)\fR and \fIc)\fR gives a recapitulation
of the basic frequency bands used in procedure\ 2 in which the through\(hyconnection
facilities described in Recommendation\ G.242 are provided.
.PP
\fINote\ 2\fR \ \(em\ The frequency band occupied by 15\(hysupergroup assembly\
No.\ 3 (8620\ to 12 | 36\ kHz) lies within the frequency band occupied
by the basic
supermastergroup (8516\ to 12 | 88\ kHz). The equipments which are used for
translating into the line\(hyfrequency band and vice versa may therefore be the
same.
.PP
For this reason, these equipments carry the same name of
\*Qsupermastergroup\(hytranslating equipment\*U.
.RT
.sp 2P
.LP
\fB2\fR \fBThrough\(hyconnection filters\fR
.sp 1P
.RT
.PP
Through\(hygroup, supergroup, etc., filters and direct
through\(hyconnection filters (see Recommendation\ G.242).
.PP
The equipment listed under the preceding sentence and \(sc\ 1 above can
be interconnected for setting up long groups, supergroups, etc., over several
carrier systems. An example of such a link is shown in Figure\ 2/G.211
together with the expressions defined below that are recommended for describing
the
various parts of a circuit on such a group or supergroup, etc.
.PP
Figure\ 3/G.211 refers to definitions\ 3.2 to\ 3.11 below.
.PP
Those of the following definitions that concern \*Qlinks\*U or
\*Qsections\*U apply, unless otherwise stated, to the combination of both
directions of transmission. A distinction between the two directions of
transmission may, however, be necessary in the case of unidirectional,
multiple\(hydesignation \*Qlinks\*U or \*Qsections\*U set up over multiple\(hydestination
telecommunication satellite systems.
.RT
.LP
.rs
.sp 28P
.ad r
\fBFigure 2/G.211, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fB3\fR \fBDefinitions\fR
.sp 1P
.RT
.sp 1P
.LP
3.1
\fBline link (using symmetric pairs, coaxial pairs, etc.)\fR
.sp 9p
.RT
.LP
\fIF:\ liaison en ligne (\*`a paires sym\*'etriques, \*`a paires coaxiales,
etc.)\fR
.LP
\fIS:\ enlace en l\*'inea (de pares sim\*'etricos, de pares coaxiales,
etc.)\fR
.PP
A transmission path, however provided, together with all the
associated equipment, such that the bandwidth available, while not having
any specific limits, is effectively the same throughout the length of the
link.
.PP
Within the link there are no direct filtration points nor any
through\(hyconnection points for groups, supergroups, etc., and the ends of the
link are the points at which the band of line frequencies is changed in some
way or other.
.RT
.sp 1P
.LP
3.2
\fBgroup link\fR
.sp 9p
.RT
.LP
\fIF:\ liaison en groupe primaire\fR
.LP
\fIS:\ enlace en grupo primario\fR
.PP
The whole of the means of transmission using a frequency band of specified
width (48\ kHz) connecting two terminal equipments, for example
channel translating equipments, wideband sending and receiving equipments
(modems, etc.). The ends of the link are the points on group distribution
frames (or their equivalent) to which the terminal equipments are connected.
.PP
It can include one or more group sections.
.RT
.sp 1P
.LP
3.3
\fBsupergroup link\fR
.sp 9p
.RT
.LP
\fIF:\ liaison en groupe secondaire\fR
.LP
\fIS:\ enlace en grupo secundario\fR
.PP
The whole of the means of transmission using a frequency band of specified
width (240\ kHz) connecting two terminal equipments, for example
group translating equipments, wideband sending and receiving equipments
(modems,\ etc.). The ends of the link are the points on supergroup
distribution frames (or their equivalent) to which the terminal equipments
are connected.
.PP
It can include one or more supergroup sections.
.RT
.sp 1P
.LP
3.4
\fBmastergroup link\fR
.sp 9p
.RT
.LP
\fIF:\ liaison en groupe tertiaire\fR
.LP
\fIS:\ enlace en grupo terciario\fR
.PP
The whole of the means of transmission using a frequency band of specified
width (1232\ kHz) connecting two terminal equipments, for example
supergroup translating equipments, wideband sending and receiving equipments
(modems,\ etc.). The ends of the link are the points on mastergroup
distribution frames (or their equivalent) to which the terminal equipments
are connected.
.PP
It can include one or more mastergroup sections.
.PP
\fINote\fR \ \(em\ As translating procedure\ 2 described under \(sc\ 1
above does not enable mastergroups to be set up, the \*Qmastergroup link\*U
concept applies only in procedure\ 1.
.RT
.sp 1P
.LP
3.5
\fBsupermastergroup link\fR
.sp 9p
.RT
.LP
\fIF:\ liaison en groupe quaternaire\fR
.LP
\fIS:\ enlace en grupo cuaternario\fR
.PP
The whole of the means of transmission using a frequency band of specified
width (3872\ kHz) connecting two terminal equipments, for example
mastergroup translating equipments, wideband sending and receiving equipments
(modems,\ etc.). The ends of the link are the points on supermastergroup
distribution frames (or their equivalent) to which the terminal equipments
are connected.
.bp
.RT
.PP
It can include one or more supermastergroup sections.
.PP
\fINote\fR \ \(em\ As the frequency band occupied by 15\(hysupergroup
assembly\ No.\ 3 (8620\ to 12 | 36\ kHz) lies within the frequency band
occupied by the basic supermastergroup (8516\ to 12 | 88\ kHz), the basic
supermastergroup
link can transmit one supermastergroup or an assembly of 15
supergroups.
.RT
.sp 1P
.LP
3.6
\fB15\(hysupergroup assembly link\fR
.sp 9p
.RT
.LP
\fIF:\ liaison en assemblage de 15 groupes secondaires\fR
.LP
\fIS:\ enlace en agregado de 15 grupos secundarios\fR
.PP
The whole of the means of transmission using a frequency band of specified
width (3716\ kHz) connecting two terminal equipments (supergroup
modems permitting the setting\(hyup of a 15\(hysupergroup assembly). The
ends of the link are the points on 15\(hysupergroup assembly distribution
frames (or their
equivalent) to which the terminal equipments are connected.
.PP
It can include one or more 15\(hysupergroup assembly sections.
.PP
\fINote\fR \ \(em\ The notion of 15\(hysupergroup assembly link relates to
translating procedure\ 2 mentioned in \(sc\ 1 above. It is the equivalent
of the
\*Qsupermastergroup link\*U concept of the translating procedure\ 1
(900\ telephone channels).
.RT
.sp 1P
.LP
3.7
\fBgroup section\fR
.sp 9p
.RT
.LP
\fIF:\ section de groupe primaire\fR
.LP
\fIS:\ secci\*'on de grupo primario\fR
.PP
The whole of the means of transmission using a frequency band of specified
width (48\ kHz) connecting two consecutive group distribution frames (or
equivalent points) via at least one line link.
.RT
.sp 1P
.LP
3.8
\fBsupergroup section\fR
.sp 9p
.RT
.LP
\fIF:\ section de groupe secondaire\fR
.LP
\fIS:\ secci\*'on de grupo secundario\fR
.PP
The whole of the means of transmission using a frequency band of specified
width (240\ kHz) connecting two consecutive supergroup distribution
frames (or equivalent points) via at least one line link.
.RT
.sp 1P
.LP
3.9
\fBmastergroup section\fR
.sp 9p
.RT
.LP
\fIF:\ section de groupe tertiaire\fR
.LP
\fIS:\ secci\*'on de grupo terciario\fR
.PP
The whole of the means of transmission using a frequency band of specified
width (1232\ kHz) connecting two consecutive mastergroup distribution frames
(or equivalent points) via at least one line link.
.PP
\fINote\fR \ \(em\ As translating procedure\ 2 described in \(sc\ 1 above
does not
enable mastergroups to be set up, the \*Qmastergroup section\*U concept applies
only in procedure\ 1.
.RT
.sp 1P
.LP
3.10
\fBsupermastergroup section\fR
.sp 9p
.RT
.LP
\fIF:\ section de groupe quaternaire\fR
.LP
\fIS:\ secci\*'on de grupo cuaternario\fR
.PP
The whole of the means of transmission using a frequency band of specified
width (3872\ kHz) connecting two supermastergroup distribution frames (or
equivalent points) via at least one line link.
.PP
\fINote\fR \ \(em\ As the frequency band occupied by 15\(hysupergroup
assembly\ No.\ 3 (8620\ to 12 | 36\ kHz) lies within the frequency band
occupied by the basic supermastergroup (8516\ to 12 | 88\ kHz), the supermastergroup
section can transmit one supermastergroup or an assembly of
15\ supergroups.
.bp
.RT
.LP
.rs
.sp 47P
.ad r
\fBFigure 3/G.211, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.11
\fB15\(hysupergroup assembly section\fR
.sp 9p
.RT
.LP
\fIF:\ section d'assemblage de 15 groupes secondaires\fR
.LP
\fIS:\ secci\*'on de agregado de 15 grupos secundarios\fR
.PP
The whole of the means of transmission using a frequency band of specified
width (3716\ kHz) connecting two consecutive 15\(hysupergroup assembly
distribution frames (or equivalent points) via at least one line link.
.PP
\fINote\ 1\fR \ \(em\ Same note as for definition\ 3.6 above.
.PP
\fINote\ 2\fR \ \(em\ In a country which uses procedure\ 1, a 15\(hysupergroup
assembly can be through\(hyconnected without difficulty at the supermastergroup
distribution frame. In this case, the 15\(hysupergroup assembly is
through\(hyconnected to position\ \fI3\fR (8620\(hy12 | 36\ kHz) instead
of position\ \fI1\fR
(312\(hy4028\ kHz) as required by the definition of the through\(hyconnection
point of such an assembly (see Recommendation\ G.242, \(sc\ 6). This through\(hyconnection
point does not therefore correspond to this definition and is not at the
end of a
15\(hysupergroup assembly section.
.RT
.sp 1P
.LP
3.12
\fBthrough\(hygroup connection point\fR
.sp 9p
.RT
.LP
\fIF:\ point de transfert de groupe primaire\fR
.LP
\fIS:\ punto de transferencia de grupo primario\fR
.PP
When a group link is made up of several group sections, they are connected
in tandem by means of through\(hygroup filters at points called
through\(hygroup connection points.
.RT
.sp 1P
.LP
3.13
\fBthrough\(hysupergroup connection point\fR
.sp 9p
.RT
.LP
\fIF:\ point de transfert de groupe secondaire\fR
.LP
\fIS:\ punto de transferencia de grupo secundario\fR
.PP
When a supergroup link is made up of several supergroup sections, they
are connected in tandem by means of through\(hysupergroup filters at points
called through\(hysupergroup connection points.
.RT
.sp 1P
.LP
3.14
\fBthrough\(hymastergroup connection point\fR
.sp 9p
.RT
.LP
\fIF:\ point de transfert de groupe tertiaire\fR
.LP
\fIS:\ punto de transferencia de grupo terciario\fR
.PP
When a mastergroup link is made up of several mastergroup
sections, they are connected in tandem by means of through\(hymastergroup
filters at points called through\(hymastergroup connection points.
.RT
.sp 1P
.LP
3.15
\fBthrough\(hysupermastergroup connection point\fR
.sp 9p
.RT
.LP
\fIF:\ point de transfert de groupe quaternaire\fR
.LP
\fIS:\ punto de transferencia de grupo cuaternario\fR
.PP
When a supermastergroup link is made up of several
supermastergroup sections they are connected in tandem by means of
through\(hysupermastergroup filters at points called through\(hysupermastergroup
connection points.
.RT
.sp 1P
.LP
3.16
\fBthrough\(hy15\(hysupergroup assembly connection point\fR
.sp 9p
.RT
.LP
\fIF:\ point de transfert d'assemblage de 15 groupes\fR
.LP
\fIS:\ punto de transferencia de agregado de 15 grupos secundarios\fR
.PP
When a 15\(hysupergroup assembly link is made up of several
15\(hysupergroup assembly sections, these sections are interconnected in
tandem by means of through\(hy15\(hysupergroup assembly filters at points
called
through\(hy15\(hy supergroup assembly connection points.
.bp
.PP
As an alternative when the 15\(hysupergroup assembly equipment provides
sufficient filtering (corresponding to the definition of through\(hyconnection
equipments\ \(em\ see Recommendation\ G.242,\ \(sc\ 6) through\(hy15\(hysupergroup
assembly
filters can be dispensed with.
.PP
\fINote\fR \ \(em\ When a 15\(hysupergroup assembly is connected by means of
through\(hysupermastergroup filters, the point of interconnection is the
through\(hysupermastergroup connection point and not a through\(hy15\(hysupergroup
assembly connection point.
.RT
.sp 1P
.LP
3.17
\fBregulated line section (symmetric pairs, coaxial pairs or
radio\(hyrelay links, etc.)\fR
.sp 9p
.RT
.LP
\fIF:\ section de r\*'egulation de ligne (\*`a paires sym\*'etriques ou\fR
\fIcoaxiales ou sur faisceau hertzien, etc.)\fR
.LP
\fIS:\ secci\*'on de regulaci\*'on de l\*'inea (de pares sim\*'etricos o\fR
\fIcoaxiales, o por radio\(hyenlaces, etc.)\fR
.PP
In a carrier transmission system, a line section on which the
line\(hyregulating pilot or pilots are transmitted from end to end without
passing through an amplitude\(hychanging device peculiar to the pilot or
pilots.
.RT
.sp 1P
.LP
3.18
\fBmain repeater station\fR
.sp 9p
.RT
.LP
\fIF:\ station principale de r\*'ep\*'eteurs\fR
.LP
\fIS:\ estaci\*'on principal de repetidores\fR
.PP
A station, always the terminal of a line link (see
definition\ 3.1\ above), where direct line filtering or demodulation or both
together may take place. As a consequence, in such a station there are
equalizers and it is possible to find points which are of uniform relative
level independent of frequency (\*Qflat points\*U).
.PP
Such a station, where all the supergroups, for example, are
demodulated and brought into the basic supergroup position, is called a
\*Qmain terminal station\*U and is of necessity at the end of a regulated\(hyline
section. A \*Qmain intermediate station\*U is a station within a regulated\(hyline
section where a direct through\(hyconnection takes place.
.RT
.sp 2P
.LP
\fBReference\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fI8\(hychannel terminal equipments\fR , Orange Book,
Vol.\ III\(hy1, Rec.\ G.234, ITU, Geneva, 1977.
.sp 2P
.LP
\fBRecommendation\ G.212\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBHYPOTHETICAL\ REFERENCE\ CIRCUITS\ FOR\ ANALOGUE\ SYSTEMS\fR
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.212''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.212 %'
.ce 0
.sp 1P
.ce 1000
\fBGENERAL\ DEFINITIONS\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBhypothetical reference circuit\fR
.sp 1P
.RT
.LP
\fIF:\ circuit fictif de r\*'ef\*'erence\fR
.LP
\fIS:\ circuito ficticio de referencia\fR
.PP
This is a hypothetical circuit of defined length and with a
specified number of terminal and intermediate equipments, this number being
sufficient but not excessive. It forms a basis for the study of certain
characteristics of long\(hydistance circuits (noise, for example).
.RT
.sp 2P
.LP
\fB2\fR \fBhypothetical reference circuit for telephony\fR
.sp 1P
.RT
.LP
\fIF:\ circuit fictif de r\*'ef\*'erence pour la t\*'el\*'ephonie\fR
.LP
\fIS:\ circuito ficticio de referencia para la telefon\*'ia\fR
.PP
This is a complete telephone circuit (between audio\(hyfrequency
terminals) established on a hypothetical international telephone carrier
system and having a specified length and a specified number of modulations
and
demodulations of channels, groups, supergroups, these numbers being reasonably
great but not having their maximum possible values. The hypothetical reference
circuit has to reflect what is generally expected to be the practical
application of the system.
.PP
Various hypothetical reference circuits for telephony have been
defined to allow the coordination of the different specifications concerning
the constituent parts of the multichannel carrier telephone systems, so that
the complete telephone circuits set up on these systems can meet CCITT
standards.
.bp
.PP
In order to take account of the variety of operating conditions and in
particular the differences there may be in the size of the countries to
be
served, the CCITT has defined two categories of hypothetical reference
circuits for telephony:
.RT
.LP
\(em
a set of hypothetical reference circuits with a length of
2500\ km,
.LP
\(em
a hypothetical reference circuit with a length of 5000 km
(see Recommendation\ G.215).
.PP
The former includes the following hypothetical reference circuits for telephony:
.LP
\(em
on open\(hywire lines (see Recommendation G.311),
.LP
\(em
on symmetric pair cable (see Recommendation G.322),
.LP
\(em
on coaxial pair cable (see Recommendations\ G.332 to G.346 of
sections\ 3.3 and 3.4).
.PP
The 5000 km hypothetical reference circuit is used in various
types of carrier systems on coaxial cable and on radio relay systems.
.PP
The CCIR also has defined the following hypothetical reference
circuits for telephony:
.RT
.LP
1)
In line\(hyof\(hysight radio\(hyrelay systems using
frequency\(hydivision multiplex, with a capacity of 12 to
60\ telephone channels or of more than 60\ telephone channels
(see Recommendation\ G.431 or CCIR Recommendations\ 391\ [2]
and\ 392\ [3]);
.LP
2)
On tropospheric\(hyscatter radio\(hyrelay systems (see
CCIR Recommendation\ 396\ [4]);
.LP
3)
For satellite systems (see CCIR
Recommendation\ 352\ [5]).
.PP
Each of these various hypothetical reference circuits has the same total length
.FS
With the exception of the hypothetical reference circuits for satellite
systems and for circuits of 5000\ km.
.FE
and they are all used in
the same way. They are only a guide for planning carrier systems.
.PP
These hypothetical reference circuits allow designers to study through
connection between different carrier systems at basic groups,
supergroups,\ etc., as discussed in Recommendation\ G.211. Moreover, when they
contain more than one pair of channel modulators and demodulators, they also
allow the designers to study an international switched connection having the
same total length.
.RT
.sp 2P
.LP
\fB3\fR \fBhomogeneous section\fR
.sp 1P
.RT
.LP
\fIF:\ section homog\*`ene\fR
.LP
\fIS:\ secci\*'on homog\*'enea\fR
.PP
A section without diversion or modulation of any channel groups, supergroups,
etc., established on the system which is being considered except for those
modulations or demodulations defined at the ends of the section.
.PP
All the hypothetical reference circuits defined above consist of
homogeneous sections of equal length [6, 9\ or 12\ sections
.FS
The number is not specified for the tropospheric\(hyscatter radio\(hyrelay
systems.
.FE
as the case
may be].
.PP
It is assumed that at the end of each homogeneous section, the
channels, groups, supergroups,\ etc., are connected through at random.
.RT
.LP
.sp 2P
.LP
\fB4\fR \fBpsophometric power\fR
.sp 1P
.RT
.LP
\fIF:\ puissance psophom\*'etrique\fR
.LP
\fIS:\ potencia sofom\*'etrica\fR
.PP
Where square law addition (power addition) of noise can be
assumed, it has been found convenient for calculations and design of
international circuits to use the idea of psophometric power as defined
below:
\v'6p'
.RT
.sp 1P
.ce 1000
psophometric power =
@ { psophometric~voltage) \u2\d } over { 00 } @
.ce 0
.sp 1P
.LP
or
.LP
psophometric power =
@ { psophometric~e.m.f.) \u2\d } over { ~\(mu~600 } @
.bp
.sp 1P
.ce 1000
.ce 0
.sp 1P
.PP
A convenient unit is the micro\(hymicrowatt or picowatt (pW), and
this equation can then be given as follows:
\v'6p'
.sp 1P
.ce 1000
psophometric power =
@ { psophometric~e.m.f.~in~mV) \u2\d } over { .0024 } @
(pW).
.ce 0
.sp 1P
.LP
.sp 1
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fI4\(hyMHz valve\(hytype systems on standardized\fR
\fI2.6/9.5\(hymm coaxial cable pairs\fR , Orange Book, Vol.\ III\(hy1,
Rec.\ G.338,
ITU, Geneva,\ 1977.
.LP
[2]
CCIR Recommendation \fIHypothetical reference circuit for radio\(hyrelay\fR
\fIsystems for telephony using frequency\(hydivision multiplex with a\fR
\fIcapacity of 12 to 60\ telephone channels\fR , Vol.\ IX, Rec.\ 391,
Dubrovnik,\ 1986.
.LP
[3]
CCIR Recommendation \fIHypothetical reference circuit for radio\(hyrelay\fR
\fIsystems for telephony using frequency\(hydivision multiplex with a\fR
\fIcapacity of more than 60\ telephone channels\fR , Vol.\ IX, Rec.\ 392,
Dubrovnik,\ 1986.
.LP
[4]
CCIR Recommendation \fIHypothetical reference circuit for trans\(hyhorizon\fR
\fIradio\(hyrelay systems for telephony using frequency\(hydivision\fR
\fImultiplex,\fR Vol.\ IX, Rec.\ 396, Dubrovnik,\ 1986.
.LP
[5]
CCIR Recommendation \fIHypothetical reference circuits for telephony
and\fR \fItelevision in the fixed satellite service\fR , Vol.\ IV, Rec.\
352,
Dubrovnik,\ 1986.
.sp 2P
.LP
\fBRecommendation\ G.213\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBINTERCONNECTION\ OF\ SYSTEMS\ IN\ A\ MAIN\ REPEATER\ STATION\fR
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.213''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.213 %'
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1964; further amended)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.PP
The CCITT finds it necessary to define separation points between various
types of equipment, both in cable systems and in radio\(hyrelay systems.
These separation points are defined below and the CCIR has adopted the
same
definitions when preparing its Recommendation\ 380\ [1] (see also
Recommendation\ G.423).
.sp 1P
.RT
.sp 2P
.LP
See definitions of Recommendation\ G.211.
.FE
\fB1\fR \fBDefinition of\fR \fR \fBtelephony input and output points for
the\fR \fBline link\fR
.sp 1P
.RT
.PP
These are points (marked\ \fIT\fR and\ \fIT\fR ` in Figure\ 1/G.213)
located in principle in a main repeater station
where the standard
conditions given below are found at the output and input of a line link
(comprising a cable system or radio link). These standard conditions permit
interconnection with other line links or with telephony equipment (including,
where appropriate, direct through\(hyconnection filters as well as translating
equipment).
.PP
At such a point,\ \fIT\fR , on the receiving side, the following
conditions apply:
.RT
.LP
1)
All the telephony groups (groups, supergroups, mastergroups, etc.) are
still assembled in the positions in the frequency spectrum
which they occupy on the line.
.LP
2)
All the line\(hyregulating, monitoring or frequency\(hycomparison pilots
on the H.F. line are, or can be, suppressed (the recommended suppression
attenuations are given in Recommendations\ G.242 and\ G.243), according
to
whether the station is at the end of a regulated\(hyline section or not
.FS
The
interconnecting point between a radio\(hyrelay system and a long cable
system is always the terminal of a regulated\(hyline section (CCIR Recommendation
381\ [2]
and hence all these pilots are suppressed at that point. For the distinction
between a \*Qshort\*U and a \*Qlong\*U cable system, see Recommendation G.423,
\(sc\ 1.2).
.FE
.
.bp
.LP
3)
The relative level of all the telephony channels is
independent of frequency, i.e. any de\(hyemphasis network is included in the
line equipment.
.LP
4)
No special suppression of additional measuring frequencies is foreseen
(CCITT Recommendation\ G.423 for cable systems,
CCIR Recommendation\ 381\ [2] for radio\(hyrelay
systems).
.PP
A similar point\ \fIT\fR ` | is defined for the sending side, where the
following conditions are met:
.LP
a)
All the telephony groups (groups, supergroups, mastergroups, etc.) are
still assembled in the positions in the frequency spectrum
which they occupy on the line, except where use is made of
direct through\(hyconnection filters provided as part of the line
equipment.
.LP
b)
[Follows from the situation at\ \fIT\fR according to condition\ 2) above.]
.LP
c)
The relative level of all the telephony channels is
independent of frequency, i.e. any pre\(hyemphasis network is included in the
line equipment.
.LP
d)
The additional measuring frequencies are transmitted.
.LP
.rs
.sp 28P
.ad r
\fBFIGURE 1/G.213, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
\fIGeneral remarks\fR
.sp 9p
.RT
.PP
\fINote\ 1\fR \ \(em\ Figure\ 1/G.213 gives an example only.
.PP
\fINote\ 2\fR \ \(em\ If the station is within a regulated line section,
provision must be made for the line\(hyregulating pilots to be passed through,
either by means of the telephony direct through\(hyconnection filter itself
or by means of a special pilot through\(hyconnection filter. To cater for
this case, and for the case where the station forms a boundary between
two regulated line
sections, a pilot input to, and output from, the line link, separate from
the telephony input and output points\ \fIT\fR and\ \fIT\fR `, should be
provided; these are points\ \fIP\fR and\ \fIP\fR ` in Figure\ 1/G.213.
.bp
.PP
\fINote\ 3\fR \ \(em\ (Applicable to all systems, irrespective of the number
of channels):
.PP
When there is direct through\(hyconnection of part of the groups,
supergroups,\ etc. with the aid of the direct through\(hyconnection filters
fitted into the line equipment for this purpose, it is up to each Administration
to
fix the relative levels at the filter access points (which are different
from the access point\ \fIT\fR and\ \fIT\fR ` mentioned above).
.PP
\fINote\ 4\fR \ \(em\ The levels at points\ \fIT\fR and\ \fIT\fR ` have
been chosen so as to permit the insertion of the various direct through\(hyconnecting
and
translating equipments which may be necessary in the main station. The
difference in level between points\ \fIR\fR and\ \fIT\fR and between points\
\fIT\fR `
and\ \fIR\fR ` allows for the cabling interconnecting these points, which
may be at some distance from each other and, in favourable circumstances,
for a
blocking filter having only a small loss in the passband.
.RT
.sp 2P
.LP
\fB2\fR \fBDefinition of the\fR \fBpoints of international connection at\fR
\fBbaseband frequencies of a radio\(hyrelay system\fR
.sp 1P
.RT
.PP
The points of international interconnection at baseband
frequencies, called\ \fIR\fR ` and\ \fIR\fR , form the input and output of a
radio\(hyrelay system, conforming to CCITT Recommendation\ G.423 and CCIR
Recommenda
tion\ 380\ [1].
.PP
At the output of the radio\(hyrelay system (point\ \fIR\fR ), the
following conditions are found in the baseband:
.RT
.LP
1)
All the telephony groups (groups, supergroups,
mastergroups,\ etc.), and the pilots (line regulating, frequency
comparison and monitoring pilots) included in the baseband are
assembled in the position in which they are transmitted, as
defined in the CCITT and CCIR Recommendations mentioned above.
.LP
2)
All the continuity and switching pilots and other signals
transmitted in a radio\(hyrelay system outside the telephony band,
inherent to the radio equipment, are suppressed in accordance
with CCIR Recommendation\ 381\ [2].
.LP
3)
Any radio\(hyrelay protection switching shall be performed as part of
the radio\(hyrelay system. With diversity reception, the
combined output of the receivers used corresponds to
point\ \fIR\fR .
.LP
4)
Any de\(hyemphasis networks are part of the radio equipment, so that
the relative levels of the telephone channels are independent
of frequency, within the limits of the tolerances stated in
Note\ 7 of CCIR Recommendation\ 380\ [1] (\(+- | \ dB relative to the
nominal value).
.PP
A similar point\ \fIR\fR ` is defined for the baseband input of a radio\(hyrelay
system, where similar conditions are to be met.
.sp 2P
.LP
\fB3\fR \fBRelative levels recommended by the CCITT at the telephony\fR
\fBoutput and input\fR (Points\ \fIT\fR and\ \fIT\fR ` in Figure\ 1/G.213)
.sp 1P
.RT
.PP
At the interconnection points\ \fIT\fR and\ \fIT\fR ` for telephony
defined in \(sc\ 1\ above, Table\ 1/G.213 shows the relative levels which are
recommended for cable systems, each of which is defined by the maximum
number of telephone channels that it can provide. (Similar levels are recommended
by the CCITT and the CCIR for radio systems of corresponding capacity\
\(em\ see
Recommendation\ G.423 and\ CCIR Recommendation\ 380\ [1].)
.PP
The cable systems to which this Recommendation applies are modern
systems with transistor equipment and to new versions of other systems
previously standardized by the CCITT.
.PP
The recommended levels at\ \fIT\fR and\ \fIT\fR ` make it possible to
insert all the translating or direct through\(hyconnecting equipment which
may be necessary; this does not define the relative levels in translating
and direct through\(hyconnecting equipment, which depend on other
considerations.
.RT
.LP
.rs
.sp 8P
.LP
.bp
.ce
\fBH.T. [T1.213]\fR
.ce
TABLE\ 1/G.213
.ce
\fBRecommended relative levels for interconnection
.ce
of various cable systems\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(54p) | cw(54p) | cw(36p) sw(30p) | cw(54p) , ^ | ^ | c | c | ^ .
{
Maximum number
of telephone channels
} Impedance (ohms) {
Relative power level per channel
at a main station
} Remarks
{
Receiving
(Point \fIT\fR
)
(dBr)
} {
Sending
(Point \fIT\fR
`)
(dBr)
}
_
.T&
cw(54p) | cw(54p) | cw(36p) | cw(30p) | lw(54p) .
24, 36, 48 150 (bal.) \(em23 \(em36
_
.T&
cw(54p) | cw(54p) | cw(36p) | cw(30p) | lw(54p) .
\ 60 120 150 (bal.) or 75 (unbal.) \(em23 \(em36
_
.T&
cw(54p) | cw(54p) | cw(36p) | cw(30p) | lw(54p) .
300 75 (unbal.) \(em23 \(em36
_
.T&
cw(54p) | cw(54p) | cw(36p) | cw(30p) | cw(54p) .
600, 960, 1200 1260 75 (unbal.) \(em23 or \(em33 \(em36 or \(em33 See note
_
.T&
cw(54p) | cw(54p) | cw(36p) | cw(30p) | cw(54p) .
2700 75 (unbal.) \(em33 \(em33 {
See also
Recommendations G.333
and J.77 [3]
}
_
.T&
cw(54p) | cw(54p) | cw(36p) | cw(30p) | cw(54p) .
3600 75 (unbal.) \(em33 \(em33 {
See also
Recommendations G.334
and J.77 [4]
}
_
.T&
cw(54p) | cw(54p) | cw(36p) | cw(30p) | cw(54p) .
10 | 00 75 (unbal.) \(em33 \(em33
.TE
.LP
\fINote\fR
\ \(em\ For 600, 960, 1200 and 1260 channel systems Administrations
have the choice between the alternative pairs of level shown for
points \fIT\fR
and \fIT\fR
` which apply in the following circumstances:
.LP
1)
\(em23 dBr at point \fIT\fR
,
\(em36 dBr at point \fIT\fR
`,
where conformity with well\(hyestablished equipment using similar levels
is necessary;
.LP
2)
\(em33 dBr at each of the points \fIT\fR
and \fIT\fR
`,
in other cases, for example, to new stations wholly equipped with
transistor equipments.
.nr PS 9
.RT
.ad r
\fBTable 1/G.213 [T1.213], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCIR Recommendation \fIInterconnection at baseband frequencies of\fR
\fIradio\(hyrelay systems for telephony using frequency\(hydivision multiplex\fR
,
Vol.\ IX, Rec.\ 380, Dubrovnik,\ 1986.
.LP
[2]
CCIR Recommendation \fIConditions relating to line regulating and other\fR
\fIpilots and to limits for the residues of signals outside the baseband\fR
\fIin the interconnection of radio\(hyrelay and line systems for telephony\fR ,
Vol.\ IX, Rec.\ 381, Dubrovnik,\ 1986.
.LP
[3]
CCITT Recommendation \fIUse of a 12\(hyMHz system for the simultaneous\fR
\fItransmission of telephony and television\fR , Vol.\ III,
Rec.\ J.73.
.LP
[4]
CCITT Recommendation \fICharacteristics of the television signals\fR
\fItransmitted over 18\(hyMHz and 60\(hyMHz systems\fR , Vol.\ III,
Rec.\ J.77.
.LP
.rs
.sp 3P
.LP
.bp
.sp 2P
.LP
\fBRecommendation\ G.214\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBLINE\ STABILITY\ OF\ CABLE\ SYSTEMS\fR
.FS
Stability of transmission is also the subject of Recommendation\ M.160 of
Volume\ IV\ [1].
.FE
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.214''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.214 %'
.ce 0
.sp 1P
.ce 1000
\fI(Mar del Plata, 1968)\fR \v'1P'
.sp 9p
.RT
.ce 0
.sp 1P
.PP
Line regulation
has a threefold purpose:
.sp 1P
.RT
.LP
1)
to keep actual line relative levels within such limits that
thermal or intermodulation noise never exceeds acceptable
values;
.LP
2)
to keep levels at the ends of regulated\(hyline sections within
such limits that regulators of the following multiplex
equipment are able to function;
.LP
3)
to ensure that regulation is precise enough to make it
generally unnecessary to provide an automatic group
regulator and/or supergroup regulator for the group,
supergroup,\ etc., links set up on a single regulated\(hyline
section.
.PP
It appears that all three objectives will be secured if levels at the end
of the longest regulated section envisaged are stabilized to \(+- | \ dB
at any frequency in the band transmitted.
.sp 2P
.LP
The CCITT therefore \fIunanimously recommends that:\fR
.sp 1P
.RT
.PP
Designers of line\(hyregulating systems take account of the daily and seasonal
variations in temperature to which the cables and repeaters are likely
to be subjected, the predictable ageing of components,
and also the nominal range of variation of power supplies, assuming that
appropriate precautions are taken in the placing of the cable, in the design
of buildings and in regulation of power supplies.
.PP
As a design objective for the residual effects of sustained power and temperature
variations, and the predictable ageing of components,
over the ranges expected in any period between two successive
manual adjustments, the change in insertion gain of a regulated\(hyline section
at any frequency in the transmitted band should not exceed 1\ dB.
.PP
For the purposes of this Recommendation, it is assumed that a
regulated\(hyline section will not be longer than a homogeneous section of the
hypothetical reference circuit applicable to the type of system considered
and that the interval between two successive manual adjustments will be
not less
than a fortnight.
.PP
The variations in gain of a regulated\(hyline section in service is also
affected by maintenance operations and
adjustments. The design objective excludes these effects.
.PP
Moreover, the dynamic stability of the regulating system should be
such that any swinging of the gain is damped and at a suitable rate as
a result of an abrupt change in pilot level. If, for example, the pilot
level is
suddenly increased by 2\ dB at the origin of the regulated\(hyline section, the
pilot level must not increase or diminish by more than 2\ dB at the end
of the regulated\(hyline section. The resulting fluctuations in pilot level
must fall off progressively.
.PP
\fINote\fR \ \(em\ It may be desirable to specify immunity of the regulating
system to interference from components of television signals when
transmitted.
.RT
.sp 2P
.LP
\fBReference\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fIStability of transmission\fR , Vol.\ IV,
Rec.\ M.160.
.LP
.sp 4
.bp
.sp 2P
.LP
\fBRecommendation\ G.215\fR
.RT
.sp 2P
.ce 1000
\fBHYPOTHETICAL\ REFERENCE\ CIRCUIT\ OF\ 5000\ km\fR
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.215''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.215 %'
.ce 0
.sp 1P
.ce 1000
\fBFOR\ ANALOGUE\ SYSTEMS\fR
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1980)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR \fBComposition of the hypothetical reference circuit\fR
.sp 1P
.RT
.PP
This hypothetical reference circuit is 5000 km long and
applies to various types of carrier systems on coaxial cable and radio\(hyrelay
systems, specially designed for very long international circuits. It has,
for each direction of transmission, a total of:
.RT
.LP
\(em
one pair of channel modulators which includes translation
from the audio\(hyfrequency band to the basic group and vice
versa;
.LP
\(em
three pairs of group modulators, each pair including
translation from the basic group to the basic supergroup and
vice versa;
.LP
\(em
six pairs of supergroup modulators, each pair including
translation from the basic supergroup to a higher order
modem and vice versa;
.LP
\(em
twelve pairs of higher order modulators, each pair providing
the necessary modulation stages to and from the line
frequency.
.PP
Figure 1/G.215 shows the principle of the hypothetical reference circuit.
.PP
This hypothetical reference circuit consists of 12 homogeneous
sections of equal length (see Recommendation\ G.212). Two homogeneous sections
may be connected in tandem without translating equipment at the junction
if the transmission system has suitable line regulating capability and
does not
introduce undesirable noise and crosstalk into any telephone channel.
.RT
.LP
.rs
.sp 10P
.ad r
\fBfigure 1/G.215, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB2\fR \fBDesign objectives for\fR
\fBcircuit noise\fR
.FS
Although the
noise objective for the 5000\ km HRC is in principle agreed, some countries
will not be soon in the position to install equipment of the desired performance,
and will continue to use existing systems on the very long national and
international circuits, according to established planning and design
practices.
.FE
.sp 1P
.RT
.PP
The same noise values as for the 2500 km HRC apply
(Recommendation\ G.222, \(sc\ 1).
.PP
\fINote\ 1\fR \ \(em\ This design objective is in line with Recommendation\
G.123, \*QCircuit noise in national networks\*U, which in \(sc\ 2.1.1 recommends
that the
line
noise in channels used to provide very long\(hydistance circuits (over
2500\ km)
should not exceed 2\ pW0p/km.
.PP
\fINote\ 2\fR \ \(em\ Designers are expected to fit their noise distribution
curves fall below all \(sc\(sc\ 1.1 and\ 1.2 of Recommendation\ G.222.
.PP
\fINote\ 3\fR \ \(em\ In applying these design objectives, \(sc\(sc\ 2.4
through\ 2.7 of Recommendation\ G.222 should be taken into account.
.bp
.PP
The subdivision of the total noise between the various sources of
noise is left entirely to the designer of the system, within the limits of
2500\ pW0p for the terminal equipment and 7500\ pW0p for the line. This
allocation is intended to permit the use of modulating equipment meeting the
maximum values recommended in Table\ 1/G.222 of Recommendation\ G.222 as
indicated in Table\ 1/G.215.
.RT
.ce
\fBH.T. [T1.215]\fR
.ce
TABLE\ 1/G.215
.T&
lw(72p) | lw(72p) | lw(42p) | lw(42p) .
.T&
lw(72p) | lw(72p) | lw(42p) | lw(42p) .
Total: 2500 pW0p
.TE
.LP
\fINote\fR
\ \(em\ This Table assumes two stages of modulation in the higher
modulator.
.nr PS 9
.RT
.ad r
\fBTable 1/G.215 [T1.215], p.\fR
.sp 1P
.RT
.ad b
.RT
.IP
\fB2.2\ General recommendations\fR
.sp 1P
.RT
.sp 2P
.LP
\fBRecommendation\ G.221\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBOVERALL\ \fR \fBRECOMMENDATIONS\ RELATING\ TO\ CARRIER\(hyTRANSMISSION | fR
\fBSYSTEMS\fR
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.221''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.221 %'
.ce 0
.sp 1P
.ce 1000
\fI(amended at Geneva, 1972 and 1980)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR \fBCharacteristics of complete circuits\fR
.sp 1P
.RT
.PP
The characteristics of complete circuits, measured between
audio\(hyfrequency terminals (overall loss in terminal service and in transit
service, frequency bands effectively transmitted and attenuation distortion,
variation of overall loss with time, phase distortion, stability,
crosstalk,\ etc.) should meet the general conditons for 4\(hywire telephone
circuits indicated in Section\ 1 of the Series\ G Recommendations.
.RT
.sp 2P
.LP
\fB2\fR \fBLinear crosstalk\fR
.sp 1P
.RT
.sp 1P
.LP
2.1
\fIOverall requirements\fR
.sp 9p
.RT
.PP
The requirements as regards crosstalk ratio between circuits in the case
of telephony are the subjects of Recommendation\ G.134\ [1] and the
Recommendation cited in\ [2]; for go\(hyto\(hyreturn crosstalk the Recommendation
cited in\ [3] applies.
.bp
.PP
As carrier transmission systems are also used for setting up
sound\(hyprogramme circuits, the relevant requirements given in the Series\ J
Recommendations should be taken into consideration. Recommendation\ J.18\ [4]
gives general guidance on how the higher crosstalk ratios appropriate to
sound\(hyprogramme transmissions are achieved in a telephone network.
.PP
In any case the near\(hyend crosstalk ratio between the two directions
of transmission at all frequencies used for the regulating and measuring
pilots on carrier systems should be not less than\ 40\ dB.
.RT
.sp 1P
.LP
2.2
\fIIntelligible crosstalk caused by intermodulation with a signal\fR
\fIwhich is a multiple of 4\ kHz\fR
.sp 9p
.RT
.PP
Intelligible crosstalk may arise between circuits by way of
intermodulation with a signal which is a multiple of 4\ kHz, e.g.\ a
line\(hyregulating pilot. A design objective is that the intelligible crosstalk
ratio in a single homogeneous section of the appropriate hypothetical reference
circuit should be not less than 74\ dB.
.RT
.sp 2P
.LP
\fB3\fR \fBNoise transmitted between interconnected systems\fR
.sp 1P
.RT
.PP
A failure or malfunction in a chain of repeaters may lead to large values
of noise in one or several signal bands being transmitted by that chain.
It is known that such high noise levels are generally caused by the operation
of particular types of automatic line regulators. Given that such high
noise
levels may be transmitted to other chain links, and may overload those
to which they are interconnected, it is desirable and recommended that
care should be
taken in the future in order to avoid such troubles.
.PP
Possible methods of dealing with this problem are described in
Supplement\ No.\ 4\ [5].
.PP
In respect of radio\(hyrelay links, it will be the concern of CCIR to
enumerate suitable precautions.
.RT
.sp 2P
.LP
\fB4\fR \fBSingle tone interference\fR
.sp 1P
.RT
.PP
The Recommendation cited in\ [6] indicates a limit for the single
tone interference level in telephone circuits. Depending on the origin
of such interferences, wide\(hyband services and non\(hytelephony services
(e.g.\ sound\(hyprogramme circuits, etc.) may also be affected. This should be
considered when defining limits for transmission systems.
.PP
Practical experience shows that broadcasting transmitters are the main
external source of single tone interference. In order to be usable under
normal environmental working conditions, the carrier transmission equipment
should be designed in such a way that it allows a certain electromagnetic
field strength in its vicinity, caused by transmitters. A figure of 0.5
to\ 0.7\ V/m within a
station should be tolerated by equipment which is installed as normally
specified and working under normal conditions. Where higher field strengths are
.PP
known to be expected, suitable screening measures in the building may have
to be adopted. Special attention should also be given to the stating cabling
including power distribution and to the wiring of distribution racks to
prevent interferences from entering the equipment via these points.
.PP
\fINote\fR \ \(em\ The Supplement No. 27 contains some information on possible
measures to reduce effects from interference and on measuring methods
concerning interference.
.RT
.sp 2P
.LP
\fB5\fR \fBTotal interference power\fR
.sp 1P
.RT
.PP
In addition to the above limitation of the single tone
interference, it should be ascertained that the total interference power in
each telephone channel within the band 300\(hy3400\ Hz, for each individual
case of interference, should be lower than\ \(em65\ dBm0.
.RT
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fILinear crosstalk\fR , Vol.\ III, Rec.\ G.134.
.LP
[2]
CCITT Recommendation \fIGeneral performance objectives applicable to
all\fR \fImodern international circuits and national extension circuits\fR
,
Vol.\ III, Rec.\ G.151, \(sc\ 4.1.
.LP
[3]
\fIIbid.\fR , \(sc\ 4.2.
.LP
[4]
CCITT Recommendation \fICrosstalk in sound\(hyprogramme circuits set
up on\fR \fIcarrier systems\fR , Vol.\ III, Rec.\ J.18.
.LP
[5]
\fICertain methods of avoiding the transmission of excessive noise\fR
\fIbetween interconnected systems\fR , Green Book, Vol.\ III\(hy2,
Supplement No.\ 4, ITU, Geneva, 1973.
.LP
[6]
CCITT Recommendation \fIGeneral performance objectives applicable to
all\fR \fImodern international circuits and national extension circuits\fR
,
Vol.\ III, Rec.\ G.151, \(sc\ 8.
.bp
.sp 2P
.LP
\fBRecommendation\ G.222\fR
.RT
.sp 2P
.ce 1000
\fBNOISE\ OBJECTIVES\ FOR\ DESIGN\ OF\ CARRIER\(hyTRANSMISSION\ SYSTEMS\fR
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.222''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.222 %'
.ce 0
.sp 1P
.ce 1000
\fBOF\ 2500\ km\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBDesign objectives in respect of noise produced by the line and\fR
\fBthe frequency division modulating equipment on hypothetical reference\fR
\fBcircuits of 2500\ km for telephony\fR
.sp 1P
.RT
.PP
In order to ensure that multichannel carrier systems on cable and on radio\(hyrelay
links shall comply with standards of performance considered as equivalent
in respect of noise, the following design objectives should apply to the
noise \fIat a zero relative level point\fR in any telephone channel having
the same composition as the hypothetical reference circuit on such systems.
.RT
.LP
.PP
1.1
To ensure adequate performance in respect of telephone speech and signalling
on cable systems, the mean psophometric noise power over one
minute shall not exceed 10 | 00 pW0p.
.sp 9p
.RT
.PP
1.2
To ensure adequate performance in respect of telephone speech and signalling
on radio\(hyrelay links:
.sp 9p
.RT
.PP
1.2.1
the mean psophometric noise power over one minute shall not exceed 10 | 00\
pW0p for more than 20% of any month;
.PP
1.2.2
the mean psophometric noise power over one minute shall not exceed 50 | 00\
pW0p for more than 0.1% of any month;
.PP
1.2.3
the unweighted noise power, measured or calculated with an
integrating time of\ 5\ ms shall not exceed 1 | 00 | 00\ pW0 (10\u6\d\
pW0) for more than\ 0.01% (10\uD\dlF261\u4\d) of any month.
.PP
\fINote\fR \ \(em\ For carrier transmission systems with one\(hyminute mean
noise power distributions which are not well defined, the inclusion of
another one\(hyminute mean noise clause would be desirable to ensure equivalent
performance for all systems. This clause would specify that:
.PP
The mean psophometric noise power over one minute shall not exceed
20 | 00\ pW0p for more than\ 3% of any month.
.PP
This clause has not been specifically included because the CCIR has
determined that for radio\(hyrelay links, the application of clauses 1.2.1
and\ 1.2.2 are sufficient to ensure, with high probability, that the additional
clause will also be satisfied.
.RT
.PP
1.3
If it is intended to use amplitude\(hymodulated voice\(hyfrequency
telegraph equipment for 50\ bauds conforming to the Series\ R Recommendations
and to obtain the quality shown in Recommendation\ F.10\ [1],
the mean nonweighted noise power over\ 5\ ms must not exceed 10\u6\d\ pW0
during
more than\ 0.001% (10\uD\dlF261\u5\d) of any month, nor more than\ 0.1% of
any hour, for cable systems and for radio\(hyrelay links.
.sp 9p
.RT
.PP
If frequency\(hymodulated voice\(hyfrequency telegraph equipment
operating at 50\ bauds is used, it is to be expected that the quality specified
in \(sc\(sc\ 1.1 and\ 1.2 respectively above will be satisfactory as far
as the
telegraph transmission is concerned.
.PP
The conditions under which the above design objectives should apply
are given in \(sc\ 2\ below.
.RT
.sp 2P
.LP
\fB2\fR \fBConditions in which the design objectives for hypothetical\fR
\fBreference circuits apply\fR
.sp 1P
.RT
.PP
2.1
The values mentioned in \(sc\ 1\ above are design objectives and it is
not intended that they should be quoted in specifications for equipment
or used for acceptance tests. The noise on a homogeneous section of an
actual
carrier system is dealt with in Recommendation\ G.226.
.sp 9p
.RT
.PP
The following Recommendations specify the conditions in which
these general objectives apply to different types of system, account being
taken of the special characteristics of each system:
.LP
\(em
symmetric pair cable systems
(Recommendation\ G.322);
.LP
\(em
symmetric pair cable \*Q12\ +\ 12\*U systems
(Recommendation\ G.326);
.LP
\(em
4\(hyMHz systems (Recommendation\ G.338\ [2]), 12\(hyMHz systems
(Recommendations\ G.332 and\ G.339), 18\ MHz systems (Recommendation\ G.334)
and
60\ MHz systems (Recommendation\ G.333) on 2.6/9.5\(hymm coaxial pairs;
.bp
.LP
\(em
systems on 1.2/4.4\(hymm coaxial pairs (Recommendations\ G.341, G.343,
G.344, G.345 and\ G.346);
.LP
\(em
radio\(hyrelay links using frequency\(hydivision multiplex
(Recommendation\ 393\ [3] of the CCIR).
.PP
In particular, Recommendation\ G.442 lays down objectives for the use of
amplitude\(hymodulation voice\(hyfrequency telegraphy used in line\(hyof\(hysight
radio\(hyrelay systems.
.PP
Tropospheric\(hyscatter radio\(hyrelay systems should meet the objectives
of this Recommendation, or other objectives, according to the circumstances
of
operation (see CCIR Recommendation\ 397\ [4]).
.PP
Other objectives are recommended for systems providing 12\ carrier
circuits on an open\(hywire pair (see Recommendation\ G.311).
.RT
.PP
2.2
Designers are expected to fit their distribution curves to fall
below both points given in \(sc\ 1.2.1 and \(sc\ 1.2.2\ above.
.PP
2.3
In connection with \(sc 1.2.2 above, the CCITT would have
preferred to indicate a figure of 100 | 00\ pW0p (average psophometric
power over one minute at a zero relative level point), not to be exceeded
during more
than\ 0.01% of any month. On account of difficulties in measurement, a
figure of 50 | 00\ pW0p for 0.1% of any month has been shown.
.PP
2.4
Within each homogeneous section of a hypothetical reference
circuit, the telephone channels will occupy the same position in relation to
each other. Within these sections, certain intermodulation products (those
of odd order) tend to add on the basis of linear addition of voltages,
but between sections it may be considered that in respect of noise a power\(hyadditive
law
applies exclusively.
.PP
In a part of a hypothetical reference circuit consisting of one or more
equal homogeneous sections, the one\(hyminute mean noise power not exceeded
during 20% of any month shall be considered to be proportional to the number
of homogeneous sections involved.
.PP
2.5
In parts of a hypothetical reference circuit consisting of one
or more equal homogeneous sections, the small percentage of any month in
which the one\(hyminute mean power may exceed the design objective for
0.1% of the time or less shall be regarded as proportional to the number
of homogeneous sections involved. This principle also applies to the objective
mentioned in
\(sc\ 1.2.3\ above.
.PP
2.6
Although in principle it is to be understood that the general
noise objectives are all\(hyembracing, in practice it is recognized that there
will be abnormalities from time to time which will result in additional
noise sources becoming evident. Often, such extra contributions can be
accommodated within the margin available within the system design. In other
cases, no
concern need be felt provided that such additional contributions are small
compared to the general objective, for example, less than 10% of the power
or probability of occurrence respectively.
.PP
In any case, all necessary precautions should be taken during the installation
and putting into service of the systems so that noises of external origin
are reduced to a negligible value of, at the most, 10% of the limits
fixed as objectives.
.PP
2.7
Recommendation\ G.223 gives the other hypotheses which are
recommended for the calculation of the noise on the hypothetical reference
circuits for telephony.
.sp 2P
.LP
\fB3\fR \fBCircuits more than 2500 kilometres long\fR
.sp 1P
.RT
.PP
3.1
The CCITT recognizes that in order to meet national and
international noise performance objectives some large countries have found
it necessary to introduce terrestrial FDM carrier transmission systems
that are
based on the hypothetical reference circuit described in
Recommendation\ G.215. The noise performance objective
for these systems corresponds approximately to 5000\ pW0p on the 2500\ km
hypothetical reference circuit instead of the 10 | 00\ pW0p mentioned in
\(sc\(sc\ 1.2.1 and 1.2.2 above. These values include the noise contributed by
multiplex equipment.
.sp 9p
.RT
.PP
3.2
The basic hypothetical reference circuit for satellite systems is defined
in CCIR Recommendation\ 352, and provisional noise objectives
appropriate to the design of such systems in consideration of the values
contained in \(sc\ 1 above, are contained in CCIR Recommendation\ 353\ [6].
.sp 2P
.LP
\fB4\fR \fBDesign objectives for noise produced by modulating equipments
and additional equipments\fR
.sp 1P
.RT
.PP
The general objectives mentioned in \(sc\ 1\ above include the noise
produced by modulating and additional equipments. The mean psophometric
power, which corresponds to the noise produced by all modulating equipment
mentioned in the
.bp
.PP
definition of the hypothetical reference circuit in question
and by all
additional equipment, should not exceed 2500\ picowatts at a zero relative
level point. This value of psophometric power refers to the whole of the
noise due to various sources (thermal noise, intermodulation, crosstalk,
power
supplies,\ etc.). Its allocation among the various equipments can to a
certain extent be left to the discretion of design engineers. However,
to ensure a
measure of agreement in the allocation chosen by different Administrations,
the maximum values given in Table\ 1/G.222 are recommended for the modulating
equipments.
.PP
The allocation of a large part of the noise to channel\(hymodulating
equipment is justified because these equipments are the most numerous in a
network and therefore are constructed as economically as possible.
.PP
For the through\(hyfilters a noise objective of a maximum of 10\ pW0p is
recommended. This value refers to the nominal band of the through\(hyconnected
groups; the noise outside that band must be considerably lower, to avoid a
significant contribution of noise to channels situated in adjacent frequency
bands.
.PP
For other units of additional equipment (regulating equipment,
equalizers, standby switching equipment, etc.) a value of about 15\ pW0p is
indicated as a guideline to the designer.
.PP
The above statement does not apply to line standby switching equipment
whose noise has to be considered together with that of the line.
.PP
The load assumption of through\(hyfilters and additional equipments
should be in line with Recommendation\ G.223, G.228 and G.230. Account
should be taken of the possible presence of additional signals outside
the nominal
frequency band arising from adjacent channels.
.RT
.LP
.rs
.sp 29P
.ad r
\fBTable 1/G.222 (maintenu) T1.222, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fICharacter error rate objective for telegraph\fR
\fIcommunication using 5\(hyunit start\(hystop equipment\fR , Vol.\ II,
Rec.\ F.10.
.LP
[2]
CCITT Recommendation \fI4\(hyMHz valve\(hytype systems on standardized\fR
\fI2.6/9.5\(hymm coaxial cable pairs\fR , Orange Book, Vol.\ III\(hy1,
Rec.\ G.338,
ITU, Geneva,\ 1977.
.LP
[3]
CCIR Recommendation \fIAllowable noise power in the hypothetical reference
circuit for radio\(hyrelay systems for telephony using frequency\fR
\fIdivision multiplex\fR , Vol.\ IX, Rec.\ 393, Dubrovnik,\ 1986.
.LP
[4]
CCIR Recommendation \fIAllowable noise power in the hypothetical\fR
\fIreference circuit for trans\(hyhorizon radio\(hyrelay systems for telephony\fR
\fIusing frequency division multiplex\fR , Vol.\ IX, Rec.\ 397,
Dubrovnik,\ 1986.
.LP
[5]
CCIR Recommendation \fIHypothetical reference circuits for telephony
and\fR \fItelevision in the fixed satellite service\fR , Vol.\ IV, Rec.\
352,
Dubrovnik,\ 1986.
.LP
[6]
CCIR Recommendation \fIAllowable noise power in the hypothetical\fR
\fIreference circuit for frequency\(hydivision multiplex telephony in the\fR
\fIfixed satellite service\fR , Vol.\ IV, Rec.\ 353, Dubrovnik,\ 1986.
\v'1P'
.sp 2P
.LP
\fBRecommendation\ G.223\fR
.RT
.sp 2P
.ce 1000
\fBASSUMPTIONS\ FOR\ THE\ \fR \fBCALCULATION\ OF\ NOISE\ ON\ HYPOTHETICAL\fR
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.223''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.223 %'
.ce 0
.sp 1P
.ce 1000
\fBREFERENCE\ CIRCUITS\ FOR\ TELEPHONY\fR
.ce 0
.sp 1P
.ce 1000
\fI(Remark of Recommendation\ G.222, Volume\ III of the\fR | Red Book,
.sp 9p
.RT
.ce 0
.sp 1P
.ce 1000
\fIamended at Geneva, 1964; further amended)\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBNominal \fR \fBmean power during the busy hour\fR
.sp 1P
.RT
.PP
To simplify calculations when designing carrier systems on cables or radio
links, the CCITT has adopted a \fIconventional\fR value to represent the
\fImean absolute power level\fR (at a zero relative level point) of the
speech plus signalling currents, etc., transmitted over a telephone channel
in one
direction of transmission during the busy hour.
.PP
The value adopted for this mean absolute power level corrected to a
zero relative level point is \(em15\ dBm0 (mean power\ =\ 31.6\ microwatts);
this is the mean with time and the mean for a large batch of circuits.
.PP
\fINote\ 1\fR \ \(em\ This conventional value was adopted by the CCIF in 1956
after a series of measurements and calculations had been carried out by
various Administrations between 1953 and 1955. The documentation assembled
at the time is indicated in\ [1]. The adopted value of about 32\ microwatts
was based on the following assumptions:
.RT
.LP
i)
mean power of 10\ microwatts for all signalling and tones
(Recommendation\ Q.15\ [2], gives information concerning
the apportionment on an energy basis of signals and
tones);
.LP
ii)
mean power of 22\ microwatts for other currents,
namely:
.LP
\(em
speech currents, including echoes, assuming a mean
activity factor of 0.25 for one telephone channel
in one direction of transmission;
.LP
\(em
carrier leaks (see Recommendations\ G.232, \(sc\ 5;
G.233, \(sc\ 11; G.235, \(sc\ 5); and the Recommendations cited
in [3] and\ [4];
.LP
\(em
telegraph signals, assuming that few telephone channels
are used for VF telegraphy systems (output signal power
135\ microwatts (the Recommendation cited in\ [5])) or
phototelegraphy (amplitude modulated signal with a
maximum signal power of about 1\ milliwatt (the
Recommendation cited in\ [6])).
.bp
.PP
On the other hand, the power of pilots in the load of modern carrier systems
has been treated as negligible.
.PP
The reference to \*Qthe busy hour\*U in \(sc\ 1 is to indicate that the
limit (of \(em15\ dBm0) applies when transmission systems and telephone
exchanges are at their busiest so that the various factors concerning occupancy
and
activity of the various services and signals are to be those appropriate to
such busy conditions.
.PP
It is not intended to suggest that an integrating period of one hour may
be used in the specification of the signals emitted by individual devices
connected to transmission systems. This could lead to insupportably high
short\(hyterm power levels being permitted which give rise to interference for
durations of significance to telephony and other services.
.RT
.PP
\fINote\ 2\fR \ \(em\ The question of reconsidering the assumptions leading
to this conventional value arose in 1968 for the following reasons:
.LP
\(em
changes in the r.m.s. power of speech signals, due to the use of more
modern telephone sets, to a different transmission plan,
and perhaps also to some change in subscriber habits;
.LP
\(em
change in the mean activity factor of a telephone channel
due, \fIinter alia\fR , to different operating methods;
.LP
\(em
increase in the number of VF telegraphy bearer circuits and sound\(hyprogramme
circuits;
.LP
\(em
introduction of circuits used for data transmission, and
rapid increase in their number.
.PP
During several Study Periods these points have been under study and various
Administrations carried out measurements of speech signal power and
loading of carrier systems. The results are shown in Supplement No.\ 5. These
results indicate that there is no sufficiently firm information to justify
an alteration to the conventional mean value of \(em15\ dBm0 (32\ \(*mW0)
for the
long\(hyterm mean power level per channel.
.PP
Indeed, the steps envisaged by Administrations to control and reduce the
levels of non\(hyspeech signals indicate a tendency to limit the effect
of
the increase in the non\(hyspeech services.
.PP
As regards the subdivision of the 32\ \(*mW into 10\ \(*mW signalling and
tones and 22\ \(*mW speech and echo, carrier leaks, and telegraphy, again
there is no evidence which would justify proposals to alter this subdivision.
.PP
As a general principle, it should always be the objective of
Administrations to ensure that the \fIactual\fR load carried by transmission
systems does not significantly differ from the \fIconventional\fR value
assumed in the design of such systems.
.RT
.PP
\fINote\ 3\fR \ \(em\ The CCITT has agreed to the following rules concerning
the maximum permissible number of VF telegraph bearer circuits:
.LP
1)
For a \fI12\(hychannel system\fR , both the load capacity and the
intermodulation requirements are determined by the statistics
of speech; hence there is no reason to limit the number of
channels in a 12\(hychannel system which may be used as VF
telegraphy bearer channels.
.LP
2)
For a \fI60\(hychannel system\fR , the load capacity is determined by
the statistics of speech but the intermodulation requirements
for a mixed VF telegraph and speech loading become controlling
when the VF telegraph bearers exceed about 30% of the total.
Hence it is possible, without change of specifications, to allow
up to 20\ channels in this system to be used for VF telegraphy.
.LP
3)
For a \fI120\(hychannel system\fR , about 12% of the total
could be allowed for VF telegraph bearers.
The number of reserve circuits for VF telegraphy is excluded
from these limits for both 60\(hy and 120\(hychannel systems. The number of
channels for these systems should be distributed more or less
uniformly throughout the line\(hyfrequency band.
.LP
4)
For \fIsystems with 300 or more channels\fR , the CCITT is not
yet able to define any specific limit, owing to the many complicated
factors such as mean power, peak power, overload capacity,
intermodulation, noise\(hyperformance and pre\(hyemphasis, which have
to be taken into consideration.
.LP
5)
For \fIgroups\fR and \fIsupergroups\fR no conclusion could be
obtained. From information available, it would be unwise, without special
consideration, to exceed two VF telegraph systems per supergroup
in a wideband system.
.bp
.LP
6)
For \fItransmission systems not exceeding 1000\ km\fR the
permissible number of telegraph systems may be increased if the power per
telegraph channel is reduced according to Table\ 1/G.223.
.LP
A similar table in respect of transmission systems longer
than 1000\ km cannot be drawn up at this time. There is evidence to suggest
that for systems considerably longer than 1000\ km a reduction in telegraph
signal
power gives rise to unacceptable levels of telegraph distortion and character
error rates.
.LP
.rs
.sp 12P
.ad r
\fBTable 1/G.223 (maintenu) T1.223, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB2\fR \fBLoading for calculation of intermodulation noise\fR
.sp 1P
.RT
.PP
2.1
It will be assumed for the calculation of intermodulation noise below the
overload point that the multiplex signal during the busy hour can be represented
by a uniform spectrum random noise signal, the mean absolute power level
of which, at a zero relative flat level point,
is given by the following formulae:
\v'6p'
.sp 9p
.RT
.sp 1P
.ce 1000
10 log
\d10
\u
\fIP\fR |
(\fIn\fR )\ =\ (\(em 15 + 10
log
\d10
\u\ \fIn\fR ) dBm0 for \fIn\fR \(>=" 240
.ce 0
.sp 1P
.LP
and
.sp 1P
.ce 1000
10 log
\d10
\u
\fIP\fR |
(\fIn\fR )\ =\ (\(em 1 + 4
log
\d10
\u\ \fIn\fR ) dBm0 for 12 \(= \fIn\fR < 240,
.ce 0
.sp 1P
.LP
.sp 1
\fIn\fR | being the total number of telephone channels in the system and
\fIP\fR |
(\fIn\fR ) the power of the random noise signal in milliwatts.
.PP
Examples are shown in Table\ 2/G.223 of the results given by these formulae
for some typical values of\ \fIn\fR .
.LP
.rs
.sp 10P
.ad r
\fBTable 2/G.223 (maintenu) T2.223, p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
These results apply only to systems without pre\(hyemphasis and using independent
amplifiers for the two directions of transmission.
.bp
.PP
2.2
For 2\(hywire systems having common amplifiers for the two
directions of transmission (\fIn\fR \ +\ \fIn\fR \ systems), it is necessary
to assume a
different conventional loading. When the relative levels are the same for
both directions of transmission the conventional load is given by the following
formulae:
\v'6p'
.sp 9p
.RT
.sp 1P
.ce 1000
10 log
\d10
\u
\fIP\fR |
(\fIn\fR )\ =\ (\(em 15 +
10 log
\d10
\u 2\fIn\fR ) dBm0 for \fIn\fR \(>=" 120
.ce 0
.sp 1P
.LP
and
.sp 1P
.ce 1000
10 log
\d10
\u
\fIP\fR |
(\fIn\fR )\ =\ (\(em 1 + 4
log
\d10
\u 2\fIn\fR ) dBm0 for 12 \(= \fIn\fR < 120,
.ce 0
.sp 1P
.LP
.sp 1
where
.LP
\fIP\fR |
(\fIn\fR ) is defined in \(sc\ 2.1 above and \fIn\fR | is the number of
channels in each direction of transmission.
.PP
2.3
When use is made of a call concentrator having the effect of
multiplying the number of circuits established on a system by a coefficient
\fIa\fR , for the determination of the conventional load, the number of
channels
should be multiplied by \fIa\fR and the activity coefficient should remain
unchanged (see also Note\ 5 below). The following formulae then replace those
given in \(sc\ 2.2 above:
\v'6p'
.sp 9p
.RT
.sp 1P
.ce 1000
10 log
\d10
\u
\fIP\fR |
(\fIn\fR )\ =\ (\(em 15 +
10 log
\d10
\u \fIan\fR ) dBm0 for \fIan\fR \(>=" 240
.ce 0
.sp 1P
.LP
and
.sp 1P
.ce 1000
10 log
\d10
\u
\fIP\fR |
(\fIn\fR )\ =\ (\(em 1 + 4
log
\d10
\u \fIan\fR ) dBm0 for 12 \(= \fIan\fR < 240,
.ce 0
.sp 1P
.LP
.sp 1
\fIn\fR | being the total number of telephone channels in the system and
\fIP\fR |
(\fIn\fR ) the power of the random noise signal in milliwatts.
.PP
\fINote\ 1\fR \ \(em\ The mean absolute power level of a uniform\(hyspectrum
random noise test signal deduced from these formulae may be used in calculating
the intermodulation noise on a hypothetical reference circuit, when there
is no overloading. It is considered that these formulae give a good approximation
in calculating intermodulation noise when \fIn\fR \ \(>="\ 60. For small
numbers of channels, however, tests with uniform\(hyspectrum random noise
are less realistic owing to the wide difference in the nature of actual
and test signals.
.PP
\fINote\ 2\fR \ \(em\ In view of the conventional character of these calculations,
it was not considered useful to take into account the power transmitted
for
programme transmissions over carrier systems. Moreover, the mean value of
0.25 was assumed for the activity factor of a telephone channel and it was
not deemed useful to study any deviations from this mean.
.PP
\fINote\ 3\fR \ \(em\ Care must be taken in interpreting the results of tests
with uniform\(hyspectrum random noise loading, especially in systems in
which the dominant noise contribution in certain channels arises from a
particular kind of intermodulation product (e.g.\ A\(emB). In such cases,
the weighting factor used in relating the performance of the channel to
that under real traffic
conditions must be carefully determined. The curve given by the transfer
function of the network used to define the conventional telephone signal
(see Recommendation\ G.227) may be used in this case to determine the weighting
factor for the wideband signal.
.PP
\fINote\ 4\fR \ \(em\ The formulae in \(sc\ 2.2 above for (\fIn\fR \ +\
\fIn\fR ) type
12\(hychannel systems are the same as those given in \(sc\ 2.1 above (4\(hywire
systems), assuming that the number of channels is doubled but that there
is no
correlation between the channel activities in each direction of transmission.
For the purposes of this assumption, the fact that in an (\fIn\fR \ +\
\fIn\fR )
system the two directions of transmission of a telephone circuit are not
active at the same moment is ignored. Calculations have shown that the
resultant error is negligible and in any case is on the safe side.
.PP
\fINote\ 5\fR \ \(em\ The formulae in \(sc\ 2.3 above are only valid in
the case when all channels are equipped with call concentrators. They are
not applicable when only some of the channels are equipped with call concentrators,
because the
distribution of these channels generally will not be uniform over the band
of the multiplex signal.
.bp
.RT
.sp 2P
.LP
\fB3\fR \fBComponent characteristics and levels\fR
.sp 1P
.RT
.PP
The values of the characteristics of circuit components and the
levels to be used in calculations will be the nominal values.
.PP
\fINote\fR \ \(em\ When specifying equipments, a reasonable margin should be
allowed for the ageing of components and for tolerances on levels, supply
voltages, temperature, etc.
.RT
.sp 2P
.LP
\fB4\fR \fBPsophometric weights\fR \fBand weighting factor\fR
.sp 1P
.RT
.PP
For calculating psophometric power, use should be made of the
\fITable of psophometer weighting for commercial telephone circuits\fR which is
given in Table\ 4/G.223.
.PP
If uniform\(hyspectrum random noise is measured in a 3.1\(hykHz band with
a flat attenuation/frequency characteristic, the noise level must be reduced
by 2.5\ dB to obtain the psophometric power level. For another bandwidth,
\fIB\fR , the weighting factor will be equal to:
\v'6p'
.RT
.sp 1P
.ce 1000
@ left ( 2.5~+~10~log~\d10~\u~ { fIB\fR } over { .1~kHz } right ) @ dB
.ce 0
.sp 1P
.LP
.sp 1
When \fIB\fR \ =\ 4\ kHz, for example, this formula gives a weighting factor of
3.6\ dB.
.sp 2P
.LP
\fB5\fR \fBCalculating noise in modulating (translating) equipments\fR
.sp 1P
.RT
.PP
(See also Recommendation G.230.)
.RT
.PP
5.1
For group, supergroup, etc., \fImodulating equipments\fR , in
calculating \fIintermodulation noise\fR (below the overload point), the
following conventional values, already accepted, will be assumed for the
load at a\fR
zero relative level point:
.sp 9p
.RT
.LP
\(em
for\ 12\(hychannel\ group
modulators:
3.3 dBm0;
.LP
\(em
for\ 60\(hychannel\ supergroup
modulators:
6.1 dBm0;
.LP
\(em
for\ 300\(hychannel\ mastergroup
modulators:
9.8 dBm0.
.PP
5.2
The mean noise power in channel translating equipments due to
interference from channels adjacent to the disturbed channel will be calculated
as follows. In all the terminal equipment of the hypothetical reference
circuit there are six exposures to adjacent\(hychannel disturbance. Five
of these
disturbing channels will be assumed to carry speech\(hylike loading signals
each having a mean power of 32\ \(*mW, i.e. an absolute power level of
\(em15\ dBm0 per
channel at a zero relative level point, while the sixth disturbing channel
will be assumed to carry telegraphy, phototelegraphy or data transmission
with a
conventional loading of 135\ \(*mW applied at the zero relative level point,
i.e. an absolute power of \(em8.7\ dBm0 uniformly distributed over the
frequency
range\ 380 to\ 3220\ Hz.
.sp 9p
.RT
.PP
The conventional telephony signal defined in Recommendation\ G.227 may
be used to simulate the speech signals transmitted on the disturbing
channels.
.PP
\fINote\fR \ \(em\ Limitation of crosstalk caused by channels adjacent to the
disturbed channel is governed by an additional clause in the channel equipment
specification (see Recommendation\ G.232, \(sc\ 9.2). In addition, the
power of
signalling pulses is restricted by Recommendation\ G.224.
.RT
.PP
5.3
In all cases allowance should, of course, be made for thermal
noise.
.sp 9p
.RT
.sp 2P
.LP
\fB6\fR \fBOverload point of amplifiers\fR , \fBthe\fR
\fBequivalent\fR
\fBr.m.s. power of the peak of the multiplex signal\fR \fBand the\fR
\fBmargin\fR \fBagainst saturation\fR
.sp 1P
.RT
.sp 1P
.LP
6.1
\fBoverload point\fR
.sp 9p
.RT
.PP
The overload point or overload level of an\fR amplifier is at that value
of absolute power level at the output at which the absolute power level
of the third harmonic increases by 20\ dB when the input signal to the
amplifier is increased by 1\ dB.
.bp
.PP
This first definition does not apply when the test frequency is so
high that the third harmonic frequency falls outside the useful bandwidth of
the amplifier. The following definition may then be used:
.RT
.LP
\fISecond definition\fR \ \(em\ The overload point or overload level of an
amplifier is 6\ dB higher than the absolute power level in dBm, at the
output of the amplifier, of each of two sinusoidal signals of equal amplitude
and of
frequencies\ A and\ B respectively, when these absolute power levels are so
adjusted that an increase of 1\ dB in both of their separate levels at
the input of the amplifier causes an increase, at the output of the amplifier,
of 20\ dB in the intermodulation product of frequency\ 2A\(emB.
.sp 1P
.LP
6.2
\fBequivalent r.m.s. sine wave power of the peak of a\fR
\fBmultiplex telephone signal\fR
.sp 9p
.RT
.PP
This is the power of a sinusoidal signal whose amplitude is that of the
peak voltage of the multiplex signal. Figure\ 1/G.223 shows the
equivalent peak power level in terms of the number of channels. Up to
1000\ channels, it is derived from Curve\ B, Figure\ 7 of Reference\ [7] taking
into account the conventional value (\(em15\ dBm0) allowed by the CCITT for the
mean power per channel instead of \(em16\ dBm0, i.e.\ an increase of 1\ dB.
Numerical values are given in Table\ 3/G.223.
.RT
.LP
.rs
.sp 8P
.ad r
\fBTable 3/G.223 (maintenu) T3.223, p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
For systems having a capacity higher than 1000 channels, the
equivalent peak power level may be derived from the following
formula:
\v'6p'
.sp 1P
.ce 1000
10 log
\d10
\u \fIP\fR \deq
\u =
@ left [ \(em5~+~10~log~\d10~\u~\fIn\fR~+~10~log~\d10~\u~ left ( 1~+ { 5 } over { sqrt { fIn\fR } } right ) right ] @ \ dBm0
.ce 0
.sp 1P
.LP
.sp 1
where
.LP
\fIP\fR\d\fIe\fR\\d\fIq\fR\u is the equivalent r.m.s. sine wave
power in milliwatts and
.LP
\fIn\fR the number of channels.
.PP
Table 3a/G.223 gives corresponding numerical values for a few
typical numbers of channels.
.PP
The curve in Figure\ 1/G.223 and the formula for numbers of channels exceeding
1000 are for use when there is no amplitude limiter at the channel
input and when there is no pre\(hyemphasis in the overall band of the multiplex
signal; other cases are being studied.
.PP
\fINote\fR \ \(em\ Mathematical models which enable calculations of the
equivalent peak power level of multiplex telephone speech signals are described
in Supplement No.\ 22 at the end of present fascicle.
.RT
.sp 1P
.LP
6.3
\fBMargin against saturation\fR
.sp 9p
.RT
.PP
In planning, a margin of a few decibels should be maintained
between the absolute level of the equivalent power of the peak of the multiplex
signal and the amplifier saturation point, to allow for level variations,
ageing,\ etc. A national practice to estimate the signal load margin of
systems and equipments is shown in Supplement No.\ 26.
.PP
\fIMultiplex signals different from telephony\fR \ \(em\ It is stressed that
\(sc\ 6.2 above relates to systems designed for telephony only, i.e. for
a channel loading as described in \(sc\ 1 above. It should be realized
that when the
characteristics of the multiplex signal differ significantly from those
assumed in \(sc\ 1 above, additional margins against saturation may be
required.
.bp
.RT
.LP
.rs
.sp 36P
.ad r
\fBFigure 1/G.223, p.\fR
.sp 1P
.RT
.ad b
.RT
.ce
\fBH.T. [T4.223]\fR
.ce
TABLE\ 3a/G.223
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(96p) | cw(24p) | cw(30p) | cw(24p) | cw(30p) | cw(24p) .
{
Number of chanel, \fIn\fR
} 1260 1800 2700 3600 10 | 00
_
.T&
lw(96p) | cw(24p) | cw(30p) | cw(24p) | cw(30p) | cw(24p) .
{
Equivalent peak power level (dBm0)
} 27.5 29 30.5 31.5 36
_
.TE
.nr PS 9
.RT
.ad r
\fBTable 3a/G.223 [T4.223] p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBTable 4/G.223 (maintenu) 1T5.223, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 34P
.ad r
\fBTable 4/G.223 (maintenu) 2T5.223, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
\fICCITT collected documents on the volume and power of speech currents\fR
\fItransmitted over international telephone circuits\fR , Blue Book, Vol.\
III,
Part\ 4, Annex\ 6, ITU, Geneva,\ 1965.
.LP
[2]
CCITT Recommendation \fINominal mean power during the busy hour\fR ,
Vol.\ VI, Rec.\ Q.15.
.LP
[3]
CCITT Recommendation \fICharacteristics of group links for the\fR
\fItransmission of wide\(hyspectrum signals\fR , Vol.\ III,
Rec.\ H.14, \(sc\ 2.3.
.LP
[4]
CCITT Recommendation \fICharacteristics of supergroup links for the\fR
\fItransmission of wide\(hyspectrum signals\fR , Vol.\ III,
Rec.\ H.15, \(sc\ 2.3.
.LP
[5]
CCITT Recommendation \fIBasic characteristics of telegraph equipments\fR
\fIused in international voice\(hyfrequency telegraph systems\fR , Vol.\ III,
Rec.\ H.23, \(sc\ 1.2.
.LP
[6]
CCITT Recommendation \fIPhototelegraph transmissions on telephone\(hytype\fR
\fIcircuits\fR , Vol.\ III, Rec.\ H.41, \(sc\ 2.3.
.LP
[7]
HOLBROOK (B. | .) and DIXON (J. | .): Load Rating Theory for Multichannel
Amplifiers, \fIBell System Technical Journal\fR , \fB18\fR , No.\ 4, pp.\
624\(hy644,
October\ 1939.
.bp
.sp 2P
.LP
\fBRecommendation\ G.224\fR
.RT
.sp 2P
.ce 1000
\fBMAXIMUM\ PERMISSIBLE\ VALUE\ FOR\ THE\ \fR \fBABSOLUTE\ POWER\ LEVEL\fR
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.224''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.224 %'
.ce 0
.sp 1P
.ce 1000
\fB(POWER\ REFERRED\ TO\ ONE\ MILLIWATT)\ OF\ A\ SIGNALLING | fR \fBPULSE\fR
.FS
This Recommendation is the same
as Recommendation Q.16\ [1]; it applies both to national and
to international signalling systems.
.FE
.ce 0
.sp 1P
.PP
The CCITT recommends that, for crosstalk reasons, the absolute power level
of each component of a short duration signal should not exceed the values
given in Table\ 1/G.224.
.sp 1P
.RT
.LP
.rs
.sp 18P
.ad r
\fBTable 1/G.224 (maintenu) T1.224, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fBReference\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fIMaximum permissible value for the absolute\fR
\fIpower level of a signalling pulse\fR , Vol.\ VI, Rec.\ Q.16.
\v'6p'
.sp 2P
.LP
\fBRecommendation\ G.225\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBRECOMMENDATIONS\ RELATING\ TO\ THE\ \fR \fBACCURACY\ OF | fR \fBCARRIER\
FREQUENCIES\fR
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.225''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.225 %'
.ce 0
.sp 1P
.ce 1000
\fI(amended at Geneva, 1964, and Mar del Plata, 1968)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR \fBAccuracy of the virtual carrier frequencies on an international
circuit or on a chain of circuits\fR
.sp 1P
.RT
.PP
As the channels of any international telephone circuit should be
suitable for voice\(hyfrequency telegraphy, the accuracy of the virtual carrier
frequencies should be such that the difference between an audio\(hyfrequency
applied to one end of the circuit and the frequency received at the other
end should not exceed 2\ Hz, even when there are intermediate modulating
and
demodulating processes.
.bp
.PP
To attain this objective, the CCITT recommends that the channel and
group carrier frequencies of the various stages should have the following
accuracies:
.RT
.ad r
Virtual channel carrier frequencies in group
\(+- | 0\uD\dlF261\u6\d
.PS 10
\ \
.ad b
.RT
.ad r
Group and supergroup carrier frequencies
\(+- | 0\uD\dlF261\u7\d
.PS 10
\ \
.vs +2p
.RT
.ad b
.RT
.PP
Mastergroup and supermastergroup carrier frequencies:
.ad r
\(em
for the 12\(hyMHz system
\(+- | | (mu | 0\uD\dlF261\u8\d
.PS 10
.ad b
.RT
.ad r
\(em
for the 60\(hyMHz system (above 12 MHz)
\(+- | 0\uD\dlF261\u8\d
.PS 10
\ \
.vs +2p
.RT
.ad b
.RT
.PP
Experience shows that, if a proper check is kept on the operation of oscillators
designed to these specifications, the difference between the
frequency applied at the origin of a telephone channel and the reconstituted
frequency at the other end hardly ever exceeds 2\ Hz if the channel has
the same composition as the 2500\(hykm hypothetical reference circuit for
the system
concerned.
.PP
Calculations indicate that, if these recommendations are followed, in
the 4\(hywire chain forming part of the hypothetical reference connection
defined in Figure\ 1/G.103
.FS
In fact, the chain considered for these calculations
comprised 16 (instead of 12) modulator/demodulator pairs to allow for the
possibility that submarine cables with equipments in conformity with
Recommendation\ G.235 might form part of the chain. No allowance was made,
however, for the effects of Doppler frequency\(hyshift due to inclusion of a
non\(hystationary satellite; values for this shift are given in CCIR
Report\ 214\ [2].
.FE
there is about 1% probability that the
frequency difference between the beginning and the end of the connection
will exceed 3\ Hz and less than 0.1% probability that it will exceed 4\
Hz.
.PP
\fINote\ 1\fR \ \(em\ In small stations, i.e. in stations which do not need
supergroup carrier frequencies, the accuracy of the group carrier may be
\(+- | 0\uD\dlF261\u6\d, which is the same as for channel carrier
frequencies.
.PP
\fINote\ 2\fR \ \(em\ The modulating frequencies appropriate to (\fIn\fR
\ +\ \fIn\fR ) systems should have the accuracies recommended in the relevant
Recommendations:
.RT
.LP
Recommendation\ G.311 for 12\(hychannel open\(hywire systems;
.LP
Recommendation\ G.361 for 3\(hychannel open\(hywire systems;
.LP
Recommendations\ G.326 and G.327\ [3] for (12\ +\ 12) cable systems.
.sp 2P
.LP
\fB2\fR \fBMeasure of alignment of the master oscillators\fR
.sp 1P
.RT
.PP
The recommendation in \(sc\ 1 above cannot be met without some measure
of alignment of the master oscillators at the various stations in which
modulation occurs.
.PP
Carrier\(hytransmission systems are formed into \*Qpartial networks\*U
extending over the whole or a part of a country. Synchronization of the
master oscillators of a partial network is ordinarily based on national
frequency
comparisons; international comparisons may be made if
necessary.
.RT
.sp 1P
.LP
2.1
\fINational frequency comparisons\fR
.sp 9p
.RT
.PP
It is necessary that, within the
same partial network of coaxial carrier systems, the master oscillators in
stations where frequencies are generated should be \*Qcoordinated\*U. This
\*Qcoordination\*U can consist of a control of one oscillator with respect to
another to give one of the following three conditions:
.RT
.LP
1)
synchronization, i.e. identical frequency and fixed phase
relationship;
.LP
2)
isochronization, i.e. identical frequency only;
.LP
3)
differential control to correct differences between the
frequencies at intervals.
.PP
Also, automatic devices can be used to give an alarm if the
difference in frequency between the checking pilot and a local oscillator
exceeds a certain fixed value.
.PP
The CCITT has not recommended any particular method of comparing or
controlling the master oscillators at different stations, and \*Qroutine
frequency comparison\*U of the master oscillators may be thought sufficient;
this comparison being followed if necessary by automatic or manual regulation,
the master oscillators in each partial network being compared periodically
with a national frequency standard, if possible.
.bp
.PP
The routine comparison of the frequencies generated by the master
oscillators is made by means of a \*Qfrequency check pilot\*U transmitted
to line for this purpose. It is not necessary to compare phases.
.RT
.sp 1P
.LP
2.2
\fIInternational frequency comparisons\fR
.sp 9p
.RT
.PP
The case may arise, either of a country that has a national
frequency standard with no facilities for
distributing it throughout the country (particularly in an area in which a
coaxial carrier system is to be set up), or of a country that has no national
frequency standard. Recommendation\ M.540\ [4], describes methods by
which such countries may obtain a standard frequency by radio, or may have a
controlled frequency sent over a telephone circuit.
.RT
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fIHypothetical reference connections\fR , Vol. III,
Rec.\ G.103, Figure\ 1/G.103.
.LP
[2]
CCITT Report \fIThe effects of doppler frequency\(hyshifts and switching\fR
\fIdiscontinuities in the fixed satellite service\fR , Vol.\ IV, Report\ 214,
Dubrovnik,\ 1986.
.LP
[3]
CCITT Recommendation \fIValve\(hytype systems offering 12 telephone\fR
\fIcarrier circuits on a symmetric cable pair [(12\ \fR +\fI\ 12) systems]\fR
, Orange
Book, Vol.\ III\(hy1, Rec.\ G.327, ITU, Geneva, 1977.
.LP
[4]
CCITT Recommendation \fIRoutine maintenance of carrier and pilot\fR
\fIgenerating equipment\fR , Vol.\ IV, Rec.\ M.540.
\v'1P'
.sp 2P
.LP
\fBRecommendation\ G.226\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBNOISE\ ON\ A\ REAL\ LINK\fR
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.226''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.226 %'
.ce 0
.sp 1P
.LP
\fB1\fR \fBCable systems\fR
.sp 1P
.RT
.PP
It should be appreciated that designers are usually concerned, not
with particular circuits or links, but with plant that will be used for the
establishment of many links. It is not practicable for the CCITT to specify
the performance of every real link that may be established, or for the
designer to contemplate changing his design to suit the various lengths
or other conditions on different real links. The CCITT has therefore defined
hypothetical
reference circuits, so that designers can be sure that, if their particular
design of plant is used throughout a real circuit made up in the same way as
a hypothetical reference circuit, the performance specified by the CCITT for
the hypothetical reference circuit will be realized on that real circuit.
.PP
A real international link usually has a different make\(hyup from that
of the hypothetical reference circuit, and often includes equipments of
different design. For each of these two reasons the performance to be expected
from real links cannot be deduced uniquely from the Recommendations relative
to
hypothetical reference circuits.
.PP
However, on a real homogeneous section it must be expected that the
noise power measured at the time of commissioning, and with a conventional
load as defined in \(sc\ 2 of Recommendation\ G.223, will be about the
same as that
calculated taking into account the particular composition of the real
homogeneous section and the real parameters as well as the implications of
Recommendation\ G.222, \(sc\ 2.6. There should be no cause for anxiety
unless the
measured noise power exceeds the calculated power by an appreciable amount,
which might indicate a fault somewhere in the equipment. In such a case,
every effort should be made to reduce the measured noise power to a value
of the same order as that calculated.
.RT
.sp 2P
.LP
\fB2\fR \fBRadio links\fR
.sp 1P
.RT
.PP
See CCIR Recommendation\ 395\ [1].
.bp
.RT
.sp 2P
.LP
\fBReference\fR
.sp 1P
.RT
.LP
[1]
CCIR Recommendation \fINoise in the radio portion of circuits to be\fR
\fIestablished over real radio\(hyrelay links for FDM telephony\fR , Vol.\ IX,
Rec.\ 395, Dubrovnik,\ 1986.
\v'2P'
.sp 2P
.LP
\fBRecommendation\ G.227\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBCONVENTIONAL\ TELEPHONE\ SIGNAL\fR
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.227''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.227 %'
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1964; amended at Mar del Plata, 1968)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR \fBPrinciple\fR
.sp 1P
.RT
.PP
For the calculation or measurement of crosstalk noise between
adjacent channels and, generally speaking, when it is desired to simulate
the speech currents transmitted by a telephone channel
.FS
Care is needed in
applying this conventional signal to simulate speech loading, since the
statistics of a Gaussian noise signal and of real speech are different. A
speech\(hysimulating generator for loading purposes is given in\ [1].
.FE
,
the CCITT recommends that a conventional telephone signal be used, the main
characteristic of which is a shaping network as a function of the frequency.
.PP
This network is defined by the following transfer coefficient as a
function of the frequency:
.RT
.LP
.rs
.sp 12P
.ad r
\fBFigure 1/G.227, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.ce 1000
@ { fIE\fR~ | } over { ~\fIV\fR~ | } @ =
@ { 8400~+~91238~\fIp\fR~\u2\d~+~11638~\fIp\fR~\u4\d~+~\fIp\fR (67280~+~54050~\fIp\fR~\u2\d) } over { 00~+~4001~\fIp\fR~\u2\d~+~\fIp\fR~\u4\d~+~\fIp\fR (36040~+~130~\fIp\fR~\u2\d) } @
.ce 0
.sp 1P
.ce 1000
.sp 1
where \fIp\fR = j
@ { fIf\fR (Hz) } over { 000~Hz } @ , \fIE\fR and \fIV\fR are defined
by Figure 1/G.227.
.ce 0
.sp 1P
.PP
.sp 1
The response curve of the network is shown in Figure\ 2/G.227, and an example
of the design is given in Figure\ 3/G.227 with relevant values.
.LP
.sp 2
.bp
.LP
.rs
.sp 22P
.ad r
\fBFigure 2/G.227, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 25P
.ad r
\fBFigure 3/G.227, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fB2\fR \fBExample of network design\fR
.sp 1P
.RT
.PP
The network is made up of three bridged\ \fIT\fR sections with a constant
characteristic impedance equal to \fIR\fR\d0\u\ ohms.
.PP
Figure 3/G.227 represents the network and indicates the values of the
various components normalized to\ \fIR\fR\d0\u.
.PP
A tolerance of \(+- | % can be allowed on the value of each component.
.PP
\fINote\fR \ \(em\ If \(*h\d1\u, \(*h\d2\u, \(*h\d3\uare the \*Qcomposite\*U
transfer
coefficients of sections\ 1, 2 and 3 respectively, we have:
\v'6p'
.RT
.LP
.sp 1
.sp 1P
.ce 1000
@ { fIE\fR~ | } over { ~\fIV\fR~ | } @ = \fIe\fR \u\\d(*h =
\fIe\fR \u\(*h
1
+\(*h
2
+\(*h
3
\d
.ce 0
.sp 1P
.LP
.sp 1
with\ \ \fIe\fR \u\(*h
1
\d =
@ { 6~+~90\fIp\fR~+~46\fIp\fR~\u2\d } over { ~+~90\fIp\fR~+~\fIp\fR~\u2\d } @
.LP
.sp 1
with\ \
\fIe\fR \u\(*h
2
\d =
@ { 0~+~11\fIp\fR } over { 0~+~\fIp\fR } @
.LP
.sp 1
with\ \
\fIe\fR \u\(*h
3
\d =
@ { 0~+~23\fIp\fR } over { 0~+~\fIp\fR } @
.LP
.sp 1
with\ \ \fIp\fR = j
@ { fIf\fR (Hz) } over { 000~Hz } @
.LP
.sp 2
.PP
Composite loss equals the insertion loss in this particular case
since the source and the load impedances are equal.
.FE
The minimum composite loss
of the complete
network lies in the vicinity of 600\ Hz and equals \fIa\fR\d0\u\ ~\ 2.9\
dB for this
example.
.PP
The curve in Figure\ 2/G.227 represents, as a function of frequency, the
composite loss
of the network in Figure\ 3/G.227 relative to the
minimum loss\ \fIa\fR\d0\u.
.RT
.sp 2P
.LP
\fB3\fR \fBSignal at the network input\fR
.sp 1P
.RT
.PP
The network may be energized either by a uniform\(hyspectrum random
noise signal or by a closely spaced harmonic series. In the latter case, the
following precautions are necessary:
.RT
.LP
1)
Spacing of the harmonics should not exceed 50\ Hz.
.LP
2)
The measuring instrument must have an adequate integrating
time with respect to the fundamental period of the harmonic series.
Types of CCITT instruments in general use, such as the
psophometer, are believed to be satisfactory in this respect.
.LP
3)
The peak/r.m.s. ratio of the signal should not exceed 3.5.
This requirement may be achieved, in the case of a particular
generator, by means of an associated phase\(hychanging network.
.LP
4)
The energizing signals (uniform\(hyspectrum random noise and
harmonic series) could lead to different results for subjective,
e.g. aural assessments at the receiving end, and such
measurements should not, therefore, involve the use of the conventional
telephone signal generator. That apparatus would be used solely for objective
measurements, in which a psophometer served as measuring instrument.
.sp 2P
.LP
\fBReference\fR
.sp 1P
.RT
.LP
[1]
CCITT \(em Question 5/C, Annex\ 2, Green Book, Vol.\ III, ITU,
Geneva,\ 1973.
.LP
.sp 1
.bp
.sp 2P
.LP
\fBRecommendation\ G.228\fR
.RT
.sp 2P
.ce 1000
\fBMEASUREMENT\ OF\ \fR \fBCIRCUIT\ NOISE\ IN\ CABLE\ SYSTEMS\fR
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.228''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.228 %'
.ce 0
.sp 1P
.ce 1000
\fBUSING\ A\ UNIFORM\(hySPECTRUM\ RANDOM\ NOISE\ LOADING\fR
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1964; further amended)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering that\fR
.sp 9p
.RT
.PP
(a)
it is desirable to measure the performance of cable
systems for frequency\(hydivision multiplex telephony under conditions closely
approaching those of actual operation;
.PP
(b)
a signal with a continuous uniform spectrum (white noise) has statistical
properties similar to those of a multiplex signal when the
number of channels is not too small;
.PP
(c)
the use of a signal with a continuous uniform spectrum to measure the performance
of such cable systems is already widespread;
.PP
(d)
it is necessary to standardize the frequencies and
bandwidths of the measuring channels to be used for such measurements;
.PP
(e)
for reasons of international compatibility it is necessary to standardize
the minimum attenuation and the bandwidth of the stop filters
which may have to be used in the white\(hynoise generator;
.PP
(f
)
the CCITT has indicated, for the planning of telephone circuits, a mean
value of signal power in the baseband of a multiplex telephone system to
be taken into consideration during the busy hour
(Recommendation\ G.223),
.sp 2P
.LP
\fIrecommends that\fR
.sp 1P
.RT
.PP
\fB1\fR
The performance of frequency\(hydivision multiplex cable systems
should be measured by means of a signal with a continuous uniform spectrum
in the frequency band used for the telephone channels.
.sp 9p
.RT
.PP
\fB2\fR
The nominal power level of the uniform spectrum test signal
should
be in accordance with the conventional load, specified in Recommendation\
G.223. If applied at the point of interconnection of the system corresponding
to
\fIT\fR ` of Recommendation\ G.213, the absolute power levels of interest
are shown in column\ 4 of Table\ 1/G.228.
.sp 9p
.RT
.PP
2.1
The sending equipment should be capable of providing, at the
output of an inserted bandstop filter, a loading level at least up to +10\ dB
relative to the nominal power level defined above.
.PP
2.2
Within the bandwidth corresponding to the baseband of the system
under test, the r.m.s. voltage of the white noise spectrum measured in
a band of about 2\ kHz should not vary by more than \(+- | .5\ dB. This
degree of spectrum uniformity should be met in the level range up to +6\
dB relative to the nominal power level, indicated in Table\ 1/G.228, column\
4.
.PP
2.3
The white noise test signal should be available at the output of the sending
equipment with a peak factor of about 12\ dB with respect to the r.m.s.
value.
.PP
\fB3\fR The nominal effective cut\(hyoff frequencies (the cut\(hyoff
frequencies
of hypothetical filters having ideal square cut\(hyoff characteristics and
transmitting the same power as the real filters) and tolerances for the
bandpass filters proposed for the various bandwidths of systems to be tested,
should be as specified in Table\ 2/G.228. To reduce the number of filters
required, compromises have been made between the nominal effective cut\(hyoff
frequency and the system bandwidth\(hylimiting frequency in some cases. The
tolerances ensure that consequent calibration errors do not exceed \(+- | .1\
dB and errors in measurement of intermodulation noise do not exceed \(+- | .2\
dB
assuming system pre\(hyemphasis of about 10\ dB.
.bp
.sp 9p
.RT
.LP
.rs
.sp 24P
.ad r
\fBTable 1/G.228 (maintenu) T1.228, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 25P
.ad r
\fBTable 2/G.228 (maintenu 1 corr. par Montage) T2.228, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.PP
3.1
The discrimination of a lowpass filter should be at least 20\ dB
at a frequency more than 10% above nominal cut\(hyoff and at least 25\ dB at
frequencies more than 20% above nominal cut\(hyoff. The discrimination of a
highpass filter should be at least 25\ dB at frequencies more than 20% below
nominal cut\(hyoff.
.PP
3.2
To limit discrimination against measuring channels, the spread of
losses introduced by any pair of highpass and lowpass filters should not
exceed 0.2\ dB over a range of frequencies which includes the upper and
lower measuring channels.
.PP
\fB4\fR
Values of the characteristics for the discrimination in each
stop\(hyband at the output of a sending equipment are given in Table\ 3/G.228.
These characteristics are intended to apply over a temperature range from
10 | (deC to\ 40 | (deC;
.sp 9p
.RT
.PP
\fB5\fR When the receiving equipment is connected directly to a sending
equipment provided with bandstop filters which only just meet the requirements
of \(sc\ 4\ above, the ratio of the noise power indicated by the receiving
equipment when the bandstop filter is bypassed, to that indicated when
the filter is in circuit, should be a minimum of 67\ dB; this requirement
applies when a
conventional load is applied. The minimum effective bandwidth of the receiver
should be 1.7\ kHz; the maximum reading of absolute noise power arising
from
leakage given by a receiver of 1.74\ kHz effective bandwidth and which just
meets the foregoing leakage requirement is \(em85.6\ dBm0p.
.sp 9p
.RT
.PP
\fB6\fR
Additional measuring channels may be provided by agreement
between the Administrations concerned.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ In Annexes\ A and\ B some general information is given on
the measuring procedures, the choice of filter characteristics, correction
methods and accuracy objectives.
.LP
.rs
.sp 32P
.ad r
\fBTable 3/G.228 (maintenu 1 corr. par Montage) T3.228, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation\ G.228)
.sp 9p
.RT
.ce 0
.ce 1000
\fBOutline of the \fR \fBwhite noise measuring method\fR
.sp 1P
.RT
.ce 0
.LP
A.1
\fIGeneral principle\fR
.sp 1P
.RT
.PP
The principal components of the measuring setup are shown in
Figure\ A\(hy1/G.228.
.RT
.LP
.rs
.sp 22P
.ad r
\fBFigure A\(hy1/G.228, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
A.2
\fIMeasuring procedures\fR
.sp 9p
.RT
.PP
Two methods for assessing the noise performance of a transmission
system are in widespread use:
.RT
.sp 1P
.LP
A.2.1
\fIMeasurement of noise power ratio (NPR)\fR
.sp 9p
.RT
.PP
The noise power ratio
\v'6p'
.RT
.ce 1000
NPR = 10 log
@ { fIW~\dA\u\fR~ | } over { fIW~\dB\u\fR~ | } @ dB =
?63\fIa\fR
.ce 0
.ad r
(A\(hy1)
.ad b
.RT
.LP
\v'7p'
.sp 1
is measured at various levels of\ \fIP\fR\d\fIs\fR\u. The r.m.s. level
meter serves as an indicator only. The value\ \fIW\fR\d\fIA\fR\uis the
noise power in the measuring
channel without taking account of the effect of frequency gaps between
groups of channels in actual operation.
.bp
.PP
In an \fIN\fR \(hychannel system the following definitions are
introduced:
.LP
\fIP\fR\d\fIs\fR\u =
\fIN\fR | (mu | fIP\fR\d\fIC\fR\\d\fIH\fR\u
.LP
\fIP\fR\d\fIC\fR\\d\fIH\fR\u =
variable signal power per channel
.LP
\fIp\fR\d\fIC\fR\\d\fIH\fR\u =
\(em15\ dBm0\ +\ ?63\fIp\fR \ =\ load level per channel
.LP
\(em15\ dBm0 is the conventional load per channel
according to Recommendation\ G.223 for
systems with \fIN\fR \ \(>="\ 240 | (mu | 63\fIp\fR \ (dB) is the excess load
relative to \(em15\ dBm0
.LP
\fIp\fR\d\fIn\fR\u =
weighted noise power level (dBm0p) measured
at point\ \fIT\fR in a 3.1\ kHz telephone channel.
.PP
The measured NPR values are usually plotted, as shown in
Figure\ A\(hy2/G.228, as a function of the excess channel loading\ ?63\fIp\fR .
.LP
.rs
.sp 20P
.ad r
\fBfigure A\(hy2/G.228, p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
The relation between NPR values measured on a channel and the
weighted noise power level referred to a zero relative level point is:
.ad r
\fIp\fR\d\fIn\fR\u =
(\(em\ NPR\ \(em\ 18.6\ \(em\ 10\ log\ k\ +\ ?63\fIp\fR ) dBm0p
(A\(hy2)
.vs +2p
.RT
.ad b
.RT
.LP
k
=
\fIB\fR /4\fIN\fR \ (\fIB\fR in kHz) is a correction factor which
takes account of the effect of the frequency gaps
between groups of channels in the transmission
system.
.PP
Table\ A\(hy1/G.228 gives examples of the correction for some N\(hychannel
systems:
.ce
\fBH.T. [T4.228]\fR
.ce
TABLE\ A\(hy1/G.228
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
\fIN\fR 300 960 2700 10 | 00
_
.T&
cw(48p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
10 log k (dB) 0.14 0.22 0.46 1.08
_
.TE
.nr PS 9
.RT
.ad r
\fBtable A\(hy1/G.228 [T4.228], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
A.2.2
\fIDirect measurement of weighted noise power level\fR
.sp 9p
.RT
.PP
With the particular choice of the effective receiver
bandwidth
.RT
.LP
?63\fIf\fR \ =\ 1.74\ kHz (=\ 3.1\ kHz | (mu | 0
\s6\(em0.25
.PS 10
),
.RT
.LP
the weighted noise power\ \fIP\fR\d\fIn\fR\uin a telephone channel is:
.LP
\fIP\fR\d\fIn\fR\u\ =\ \fIW\fR\d\fIB\fR\u(see Figure\ A\(hy1/G.228)
.LP
and the weighted noise level\ \fIp\fR\d\fIn\fR\ureferred to a point of
zero relative level becomes:
\v'6p'
.ce 1000
\fIp
\dn\u\fR =
@ left [ 10~log~ { fIW~\dB\u\fR } over { ~mW } +~\fIn\fR~\d2\u (dBr) right ] @
dBm0p
.ce 0
.ad r
(A\(hy3)
\v'7p'
.ad b
.RT
.PP
.sp 1
In this case the receiver (component\ 7 of Figure\ A\(hy1/G.228) must be
a calibrated power level meter.
.sp 1P
.LP
A.3
\fIExamples of investigations using the white noise measuring\fR
\fImethod\fR
.sp 9p
.RT
.PP
Two kinds of investigations can be made on a system (with
length\ \fIL\fR ) between flat relative level points\ \fIT\fR ` and\ \fIT\fR
. The
one [case\ a)] investigates the effect on the noise performance of load
deviations at the input of the system, whereas the other [case\ b)] indicates
the influence of level misalignments along the transmission line:
.RT
.LP
a)
The test signal noise power\ \fIP\fR\d\fIs\fR\uis varied and the
weighted noise level\ \fIp\fR\d\fIn\fR\uis determined in dBm0p. The result is
plotted as indicated in Figure\ A\(hy3/G.228.
.LP
Alternatively to the indication of the noise level for system length\
\fIL\fR in dBm0p, the noise power could have been
indicated in pW0p/km.
.LP
.rs
.sp 29P
.ad r
\fBfigure A\(hy3/G.228, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
b)
The relative levels on the transmission line are varied
by insertion of attenuators \(em?63\fIn\fR and\ +?63\fIn\fR at the input
and output of the system as is illustrated in Figure\ A\(hy4/G.228
which is an excerpt of Figure\ A\(hy1/G.228.
.LP
.rs
.sp 8P
.ad r
\fBfigure A\(hy4/G.228, p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
The test signal noise power\ \fIP\fR\d\fIs\fR\uis set to the conventional
value (\(em15\ dBm0/4\ kHz) at point\ \fIT\fR ` and is kept constant. The
noise power
level in
the measuring channel is determined at point\ \fIT\fR as a function of
the relative level at the repeater output, for example. The result is plotted
as shown in
Figure\ A\(hy5/G.228.
.LP
.rs
.sp 17P
.ad r
\fBfigure A\(hy5/G.228, p.\fR
.sp 1P
.RT
.ad b
.RT
.ce 1000
ANNEX\ B
.ce 0
.ce 1000
(to Recommendation G.228)
.sp 9p
.RT
.ce 0
.ce 1000
\fBMeasuring accuracy considerations affecting\fR
.sp 1P
.RT
.ce 0
.ce 1000
\fBthe design of the measuring equipment\fR
.ce 0
.LP
B.1
\fIIntroduction\fR
.sp 1P
.RT
.PP
The Recommendations relating to the measurement of circuit noise in systems
artificially loaded with uniform spectrum random noise simulating FDM telephone
signals were agreed after carefully coordinated studies by three CCI Study
Groups concerned. The different Recommendations provided for the
application of the white noise measuring method to cable systems (CCITT
Recommendation\ G.228), radio\(hyrelay systems (CCIR Recommendation\ 399\ [1]),
satellite systems (CCIR Recommendation\ 482\ [2]) and translating equipments
(CCITT Recommendation\ G.230). The objective of the coordination was that the
separately recommended measuring equipments should conform with common
measuring accuracy objectives and, as far as possible, be compatible and
interchangeable.
.bp
.PP
The overall accuracy objective of the measuring equipment when used for
routine maintenance measurements is \(+- | \ dB. A higher accuracy of about
\(+- | \ dB is desirable when measurements are made for the purpose of
assessing the noise performance of a system in relation to required performance.
This can be
achieved by following certain procedures and applying corrections as described
in B.4\ and B.5\ below.
.PP
This Annex states how certain characteristics of measuring equipments
were related to measuring accuracy objectives; any future extensions of the
Recommendations to provide for measurements on new transmission systems,
as yet unstandardized, should take account of those relationships.
.RT
.sp 2P
.LP
B.2
\fIBandstop filters\fR
.sp 1P
.RT
.sp 1P
.LP
B.2.1
\fIChoice of centre frequencies\fR
.sp 9p
.RT
.PP
In all cases the choice of nominal centre frequencies of
band\(hyelimination filters (i.e. of measuring channels) should take account of
the need to minimize the combined discrimination of the pair of bandpass
filters used when the bandstop filter provides a lower or upper measuring
channel. Therefore, as a rule the centre frequency of a lower measuring
channel should be at least 15%\ above the effective cut\(hyoff frequency
of the highpass
filter and the centre frequency of an upper measuring channel should be
more than approximately 5%\ below the cut\(hyoff frequency of the lowpass
filter
involved. Under \(sc\ 3.2 of the text of this Recommendation it is prescribed
that \*Qthe spread of losses introduced by any pair of highpass and lowpass
filters
should not exceed 0.2\ dB over a range of frequencies which includes the
outer measuring channels\*U.
.RT
.sp 1P
.LP
B.2.2
\fILeakage\fR
.sp 9p
.RT
.PP
The discrimination of a bandstop filter in the neighbourhood of the centre
frequency determines, jointly with the receiver selectivity the smallest
noise\(hyto\(hysignal ratio that can be measured accurately, i.e. the \*Qleakage\*U
effect. The bandstop filter discrimination of 70\ dB (Table\ 3/G.228) results
in a ratio of the order of \(em67\ dB being measured when the noise is
actually
negligible. Leakage effect in the receiver is adequately limited by requiring
(see \(sc\ 5 in the text of the Recommendation) that the NPR value should
be a
minimum of 67\ dB when connected directly to a send equipment with bandstop
filters which only just meet the discrimination requirements of Table\
3/G.228 and when a conventional load of \(em15\ dBm0/4\ kHz is applied.
.PP
\fINote\fR \ \(em\ According to Formula (A\(hy2) of Annex\ A this value of
NPR\ =\ 67\ dB corresponds to a residual noise level of \(em85.6\ dBm0p
(i.e.\ 2.8\ pW0p) at the most.
.RT
.sp 1P
.LP
B.2.3
\fIEffective bandwidth\fR
.sp 9p
.RT
.PP
The basic requirement for the stopband is the condition that the
discrimination should be at least 70\ dB in a bandwidth of at least 3\
kHz. The effective bandwidths (approximately the 3\(hydB points) recommended
in
Table\ 3/G.228 have been found to be technically feasible and lie in the
order of 5% or less of the system bandwidth with coil\(hycapacitor type
filters and are less than 0.5% with crystal\(hytype filters. It would present
economic
difficulties to reduce the relative bandwidth of the coil\(hytype filters or to
increase the relative bandwidth of the crystal\(hytype filters.
.RT
.sp 1P
.LP
B.2.3.1
\fIThird order nonlinearity products\fR
.sp 9p
.RT
.PP
The attenuation of the noise loading signal in the vicinity of the
measuring channel introduced by a bandstop filter causes an under\(hyindication
reading, erring on the low side, of third order nonlinearity noise power in
that measuring channel. This under\(hyindication is directly proportional
to the effective bandwidth of the elimination filter.
.PP
Assuming that procedures B.4.3\ and B.4.4\ below are both observed, the
under\(hyindication of third order products in a system using no pre\(hyemphasis
is about 0.05\ dB for a top measuring channel filter, the effective bandwidth
of
which is 1% of the system bandwidth. The error associated with a particular
filter is at its maximum when the filter provides the top measuring channel
of a system. When the same filter is used in wider band systems (thus
corresponding to an intermediate measuring channel of the system) its bandwidth
is a smaller proportion of the system bandwidth and the associated error
is
smaller.
.PP
When pre\(hyemphasis is used but total signal power is unchanged the error
is increased by the ratio of the signal density near the measuring channel
of the pre\(hyemphasized system to that of the system without pre\(hyemphasis.
.bp
.PP
The effective bandwidths of crystal\(hytype bandstop filters are so small
that their effect on measurement errors is negligible.
.PP
The recommended effective bandwidths for coil\(hycapacitor bandstop filters
(Table\ 3/G.228) are such that the under\(hyindication of third order nonlinear
noise powers, when the filters provide top measuring channels of systems
without pre\(hyemphasis, falls in the range 0.25\ to 0.30\ dB. This range
of errors becomes 0.60\ to 0.90\ dB for systems emphasized by 8\ to 10\
dB as is the case in FDM radio\(hyrelay systems (CCIR Recommendation\ 275\
[3]) or in wideband systems
on coaxial cables.
.RT
.sp 1P
.LP
B.2.3.2
\fISecond order nonlinearity products\fR
.sp 9p
.RT
.PP
In long transmission systems third order nonlinearity products
normally form a more significant proportion of the total system noise than
those of second order. For this reason the recommended maximum effective
bandwidths of bandstop filters have been determined on the basis of
accuracy objectives for the measurement of third order nonlinearity products.
.PP
Nevertheless, measuring equipments may still be used for investigations
of cases where second order nonlinearity products dominate. Corrections
for
known filter bandwidths may be made on the following basis:
.RT
.LP
a)
Again assuming that procedures B.4.3\ and B.4.4\ below are observed,
the error in a reading of second order nonlinearity
products introduced by the bandstop filter is an excess
reading, rather than the under\(hyindication in the case of
third order nonlinearity products.
.LP
b)
The excess reading is directly proportional to the effective
bandwidth of the bandstop filter expressed as a percentage
of the system bandwidth. The approximate proportionality,
assuming no system pre\(hyemphasis:
.LP
\(em
for measuring channels located near the lower limit of the
system bandwidth, an effective bandwidth of\ 1% system
bandwidth causes an excess reading of 0.05\ dB for
second order intermodulation noise power;
.LP
\(em
for measuring channels located in the middle, or near the
upper limit, of the system bandwidth, an effective
bandwidth of\ 1% system bandwidth causes an excess
reading of 0.1\ dB.
.LP
c)
The effect of system pre\(hyemphasis in the case of a bandstop
filter near the lower limit of the system bandwidth,
i.e.\ where the density of second order nonlinearity products
tends to be greatest, is to reduce the error attributable to
a given filter bandwidth in the same proportion that the
signal density at that frequency is reduced by pre\(hyemphasis.
.sp 1P
.LP
B.3
\fIBandpass filters\fR
.sp 9p
.RT
.PP
In order to reduce the number of different filters, compromises have been
made in some cases between the nominal effective cut\(hyoff frequency and
the system bandwidth limiting frequency (cf. \(sc\ 3 of the text).
.PP
For the larger systems there may also be a significant difference
between the frequency bandwidth 4\fIN\fR \ kHz (\fIN\fR \ being the system
capacity
expressed in telephone channels) and the system bandwidth (Table\ 2/G.228).
.PP
Both these facts are taken into account by the correction factor\ k
introduced in equation\ (A\(hy2) of Annex\ A and in Table\ A\(hy1/G.228.
.PP
The recommended tolerances on the nominal values of cut\(hyoff frequencies
are such that the actual and nominal bandwidths of the signal load cannot
differ by more than\ 1%. This ensures that calibration errors (in NPR
measurements) due to this particular imperfection do not exceed
about\ 0.05\ dB.
.PP
The tolerances on the effective lowpass cut\(hyoff frequencies are in all
cases less than\ 1.0% of the nominal system bandwidth and in most cases
less
than\ 0.8%. A difference of\ 0.8% leads to an error, in third order nonlinearity
noise measurement, of\ 0.1\ dB, this allowing for a pre\(hyemphasis of\
8\ dB. Even
allowing for a greater degree of pre\(hyemphasis, the maximum error from this
cause should not exceed 0.15\ dB.
.bp
.RT
.sp 2P
.LP
B.4
\fIProcedures for high accuracy measurements\fR
.sp 1P
.RT
.PP
The following measuring procedures are recommended for high accuracy type
of measurements, for example checks that transmission system noise
performance objectives are being achieved.
.RT
.sp 1P
.LP
B.4.1
\fISignal load adjustment\fR
.sp 9p
.RT
.PP
The loading power should be adjusted to the nominal value by means of a
true r.m.s. level measuring device. The maximum error, including reading
error, should not exceed \(+- | .15\ dB.
.RT
.sp 2P
.LP
B.4.2
\fIReceiver calibration\fR
.sp 1P
.RT
.PP
B.4.2.1
Using the NPR method (\(sc\ A.2.1) the receiver should
be set with reference to the received signal immediately before insertion
of a bandpass filter.
.sp 9p
.RT
.PP
B.4.2.2
Using the direct noise power measuring method (\(sc\ A.2.2) the
receiver calibration error could be decreased to \(+- | .15\ dB at the
particular
measuring slot by checking the reading with the aid of a white noise signal
and a d.c.\(hycalibrated true r.m.s. level meter.
.PP
\fINote\fR \ \(em\ The accuracy of measurements related to the zero relative
level point (dBm0p or pW0p) also depends on how precisely the relative
level at the measuring point (\fIn\fR\d2\uof Figure\ A\(hy1/G.228) is known.
.sp 1P
.LP
B.4.3
\fIInsertion of bandstop filters\fR
.sp 9p
.RT
.PP
Only one bandstop filter should be inserted at a time. This limits
errors in measurement of intermodulation noise.
.RT
.sp 1P
.LP
B.4.4
\fIReadjustment of signal load\fR
.sp 9p
.RT
.PP
Normally, the signal load should be readjusted to the nominal value after
the insertion of a bandstop filter. When measurements are specifically
to investigate second\(hyorder intermodulation, or when this is known to
dominate,
greater accuracy is obtained by readjusting only for the specified passband
insertion loss of the bandstop filter and not for the loss of spectrum
energy in the measuring slot.
.PP
\fINote\fR \ \(em\ The effect of the measuring slot bandwidth is negligible
with crystal\(hytype bandstop filters.
.RT
.sp 2P
.LP
B.4.5
\fIMeasurement at the receiver\fR
.sp 1P
.RT
.PP
B.4.5.1
Using the NPR method the noise power ratio is now measured as the change
required in the setting of an attenuator (?63\fIa\fR in
Figure\ A\(hy1/G.228) to restore the pointer of the indicating instrument
to the
original setting.
.sp 9p
.RT
.PP
B.4.5.2
Using the direct measuring method the weighted noise level can be read
in dBmp (or\ pWp) from the instrument. Optional means may be provided,
e.g.\ to shift the calibration by setting a switch to the relative level\
\fIn\fR\d2\uof the measuring access point\ \fIT\fR so that the dBm0p or
pW0p values are
indicated.
.sp 2P
.LP
B.5
\fICorrections for high accuracy measurements\fR
.sp 1P
.RT
.PP
The effects of the following error sources can be reduced by applying corrections
to the measured values:
.RT
.sp 1P
.LP
B.5.1
\fIReceiver calibration in connection with NPR method\fR
.sp 9p
.RT
.sp 1P
.LP
B.5.1.1
\fIIrregularity of the noise source\fR
.sp 9p
.RT
.PP
The tolerance for the spectrum regularity is \(+- | .5\ dB. A calibration
table (or curve) should be available for each noise generator.
.bp
.RT
.sp 1P
.LP
B.5.1.2
\fIErrors of effective system bandwidth\fR
.sp 9p
.RT
.PP
A correction in the conversion of NPR values into noise levels
(in\ dBm0p) by application of the correction factor\ k in equation\ (A\(hy2)
allows first, for the difference between nominal occupied bandwidth of the
system under test and actual bandwidth\ \fIB\fR between bandpass filter
effective
cut\(hyoff frequencies and secondly, for the difference between nominal
occupied bandwidth and the total bandwidth actually occupied by telephone
channels
(i.e. 4\fIN\fR \ kHz).
.RT
.sp 1P
.LP
B.5.1.3
\fIPassband attenuation distortion of bandpass filters at the\fR
\fImeasuring frequency\fR
.sp 9p
.RT
.PP
The corrections in \(sc\(sc B.5.1.1 and B.5.1.2 should ensure calibration
to an accuracy of\ \(+- | .2\ dB.
.RT
.sp 1P
.LP
B.5.2
\fIBandstop filter effects\fR
.sp 9p
.RT
.PP
If coil\(hycapacitor type bandstop filters are used, it might be
worthwhile to assess the error of the measured intermodulation noise due
to the effective bandwidth of these filters. To this end the rules quoted
in
B.2.3.1\ and B.2.3.2\ above should be applied.
.PP
Approximate corrections for this error are thus possible when the
proportion of third\(hy and second\(hyorder intermodulation noise has been
determined.
.RT
.sp 2P
.LP
B.6
\fILimitations of the noise loading measurement technique\fR
.sp 1P
.RT
.PP
B.6.1
Very low noise levels of less than about\ \(em83\ dBm0p
(about\ 5\ pW0p)
cannot be expected to be measured with an error of less than\ 2\ dB, where the
inherent noise leakage of the white noise measuring set is at the limit
corresponding to NPR\ \(>="\ 67\ dB as explained in B.2.2\ above.
.sp 9p
.RT
.PP
B.6.2
Although the measurements made at the specified frequencies may
confirm that the design objectives are met, the noise performance of a
system between these frequencies cannot always be inferred accurately from
these measurements. Whether this interpolation is justified or not has to be
established for the system under consideration. An approximate indication of
the frequency dependency can be gained from the frequency characteristic
of the basic noise (without loading) which can be measured with the aid
of a selective level meter and continuously varying the frequency. The
total noise performance of a system may be evaluated, when necessary, by
carrying out measurements
using additional test equipment.
.sp 2P
.LP
\fBBibliography on accuracy of white noise measuring methods\fR
.sp 1P
.RT
.LP
MUELLER\ (M.): Noise loading test errors due to finite slot width,
\fIData and Communications design\fR , pp.\ 20\(hy24, March\(hyApril\ 1973.
.LP
SPINDLER\ (W.): Noise loading measuring procedures and error sources,
\fITelecommunications\fR , pp.\ 32C\(hy32F, July\ 1974.
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCIR Recommendation \fIMeasurement of noise using a continuous uniform\fR
\fIspectrum signal on frequency\(hydivision multiplex telephony\fR \fIradio\(hyrelay
systems\fR , Vol.\ IX, Rec.\ 399, Dubrovnik,\ 1986.
.LP
[2]
CCIR Recommendation \fIMeasurement of performance by means of a signal\fR
\fIof a uniform spectrum for systems using frequency\(hydivision multiplex\fR
\fItelephony in the fixed\(hysatellite service\fR , Vol.\ IV, Rec.\ 482,
Dubrovnik,\ 1986.
.LP
[3]
CCIR Recommendation \fIPre\(hyemphasis characteristic for frequency\fR
\fImodulation radio\(hyrelay systems for telephony using frequency\(hydivision\fR
\fImultiplex\fR , Vol.\ IX, Rec.\ 275, Dubrovnik,\ 1986.
.bp
.LP
.sp 2P
.LP
\fBRecommendation\ G.229\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBUNWANTED\ MODULATION\ AND\ PHASE\ JITTER\fR
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.229''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.229 %'
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1972, further amended)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR \fBUnwanted modulation by harmonics of the power supply and other\fR
\fBlow frequencies\fR
.sp 1P
.RT
.sp 1P
.LP
1.1
\fIRequirements on carrier transmission systems\fR
.sp 9p
.RT
.PP
To enable the limit indicated in the Recommendation cited in [1] to be
met, it is recommended that a minimum side component attenuation of 45\
dB should be obtained when a signal is transmitted over a channel having
the same composition as the 2500\ km hypothetical reference circuit for
the system
concerned.
.PP
This limit is subdivided as indicated in \(sc\(sc 1.2 and 1.3 below into
allocations to terminal and to line equipment.
.RT
.LP
.sp 1P
.LP
1.2
\fICombined effect due to all translating equipment\fR
.sp 9p
.RT
.PP
The combined effect due to all translating equipment on the
hypothetical reference circuit should correspond to a minimum side component
attenuation of 48\ dB.
.PP
For each translating equipment, send and receive side taken
separately, and measured at the signal output, a side component attenuation
of at least 63\ dB should be obtained under normal operating conditions.
Under
adverse power supply conditions a minimum of 60\ dB should be met. It is
expected that then an overall value of 48\ dB, indicated above, will only
rarely be exceeded.
.PP
\fINote\fR \ \(em\ The above requirements are derived from the hypothetical
reference circuits for the 4\ MHz, 12\ MHz and 60\ MHz systems. The same
figures may be applied to other systems provided that their hypothetical
reference
circuit does not differ significantly from those referred to above.
.RT
.LP
.sp 1P
.LP
1.3
\fICombined effects due to all line equipment\fR
.sp 9p
.RT
.PP
The combined effects due to all line equipment on the hypothetical reference
circuit should correspond to a minimum side component attenuation of 48\
dB.
.PP
Line equipments can be subject to two types of interference which
will cause side components on a transmitted signal:
.RT
.LP
\(em
Effects from power supplies (for example, a residual mains
frequency ripple may be superimposed on the d.c. power feeding
current). These are potentially systematic on the complete
length of the circuit.
.LP
\(em
Effects from voltages caused by induction (for example, from
railway traction currents). They are not expected to occur
as systematically as the effects from the power supplies.
.PP
The influence caused by \fIpower supply ripple\fR should be such that a
minimum side component attenuation of 51\ dB is observed for the combined
effect of all line equipment on the hypothetical reference circuit. It
is recommended that on a single power feeding section, the side component
attenuation should not be less than 51\ +\ 10\ log\ k\ dB, where k is the
number of power feeding
sections on the hypothetical reference circuit.
.PP
\fINote\fR \ \(em\ Based on the assumptions that some power feeding sections
may be powered from battery supplies and that adverse cumulation over the
full
length of the hypothetical reference connection is unlikely, it can be
expected that the limit of 51\ dB will be observed with a high probability.
.PP
The influence caused by \fIinduced voltages\fR should be such that a
minimum side component attenuation of 51\ dB is observed for the combined
effects of all line equipment on the hypothetical reference circuit. However,
voltages caused by induction vary considerably with time. The effect of
a
source of induction is very often confined to one power feeding section. It
seems very unlikely that the induced voltage reaches its maximum value
in more than one section at the same instant.
.PP
It is recommended that the r.m.s. value of the longitudinal voltage in
a power feeding section caused by induction under normal operating conditions
(excluding short circuits and arcing on railways,\ etc.) should not exceed
150\ volts. (This limit has been recommended regarding safety aspects and is
contained in\ [2]. It seems reasonable to adopt the same value for the
present purpose.)
.bp
.PP
Calculations indicate that an allowance of 6\ dB for the combined
effect of several sections under the influence of induction should cover the
majority of likely cases. It is therefore recommended that a minimum side
component attenuation of 57\ dB should be observed on a power feeding section
under the influence of the maximum allowed induced voltage. It is estimated
that then the value of 51\ dB on a circuit of 2500\ km would only be exceeded
in rare circumstances and infrequently, particularly in view of the fact
that only a fraction of the total length would be exposed to interference
by
induction.
.RT
.sp 2P
.LP
\fB2\fR \fBPhase jitter due to translating equipments\fR
.sp 1P
.RT
.PP
For each translating equipment, send and receive sides taken
separately, a phase jitter on a signal should not exceed 1\(de peak\(hyto\(hypeak
when measured on the output of the equipment. The measurement should be
of all
phase jitter components on each side of the signal in the frequency band
20\(hy300\ Hz, i.e.\ equivalent to the frequency band indicated in
Recommendation\ 0.91\ [3].
.PP
\fINote\ 1\fR \ \(em\ The above requirement is derived from a consideration of
data signals on a telephone\(hytype circuit over a 2500\(hykm hypothetical
reference circuit. Conforming to this requirement will ensure a high probability
that the overall phase jitter from this source will not exceed 6\(de peak\(hyto\(hypeak.
This
performance will also ensure a high probability that for telephone speech
transmission the phase jitter will be below the detection threshold of a
majority of listeners.
.PP
\fINote\ 2\fR \ \(em\ In practice it is expected that phase jitter of the
magnitude given above will occur only on translating equipments using high
frequency carriers and that correspondingly lower phase jitter will be
caused by translating equipment using lower frequency carriers.
.PP
\fINote\ 3\fR \ \(em\ Where the phase jitter is caused mainly by random
noise a peak\(hyto\(hypeak/r.m.s. ratio of\ 10 should be assumed.
.RT
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fIGeneral performance objectives applicable to
all\fR \fImodern international circuits and national extension circuits\fR
,
Vol.\ III, Rec.\ G.151, \(sc\ 7.
.LP
[2]
CCITT manual \fIDirectives concerning the protection of telecommunication\fR
\fIlines against harmful effects from electricity lines\fR , Chapter\ IV,
\(sc\(sc\ 6, 7 and\ 71, ITU, Geneva,\ 1963, 1965, 1974,\ 1978.
.LP
[3]
CCITT Recommendation \fIEssential clauses for an instrument to measure\fR
\fIphase jitter on telephone circuits\fR , Vol.\ IV, Rec.\ O.91.
\v'1P'
.IP
\fB2.3\fR \ \fBTranslating equipment used on various carrier\(hytransmission\fR
\fBsystems\fR \v'6p'
.sp 1P
.RT
.sp 2P
.LP
\fBRecommendation\ G.230\fR
.RT
.sp 2P
.ce 1000
\fBMEASURING\ METHODS\ FOR\ \fR \fBNOISE\ PRODUCED\ BY\ MODULATING\ EQUIPMENT\fR
.EF '% Fascicle\ III.2\ \(em\ Rec.\ G.230''
.OF '''Fascicle\ III.2\ \(em\ Rec.\ G.230 %'
.ce 0
.sp 1P
.ce 1000
\fBAND\ THROUGH\(hyCONNECTION\ FILTERS\fR
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1976 and 1980)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.PP
Considering the provisions of Recommendation\ G.222, \(sc\ 4 and the
assumptions for the calculation of noise of Recommendation\ G.223, the
following methods for measuring the noise produced by modulating equipments
are
recommended:
.sp 1P
.RT
.sp 2P
.LP
\fB1\fR \fB12\(hychannel translating equipments\fR
.sp 1P
.RT
.PP
For the measurement of noise produced by 12\(hychannel translating
equipments, eleven incoherent noise random signals with a normal
(Gaussian)
.bp
.PP
level distribution and with a power distribution according to Recommendation\
G.227 should be used. As a provisional value, the peak/r.m.s. ratio of
each of the noise signals should be about 12\ dB. The allocation
on the 12\(hychannel inputs of the conventional load of 2140\ \(*mW0 (+3.3\
dBm0)
should be as follows:
.RT
.ad r
1 channel being measured
\ \ \ 0\ \(*mW0
.ad b
.RT
.ad r
2 adjacent channels at 32 \(*mW0 (\(em15 dBm0) each
\ \ 64\ \(*mW0
.ad b
.RT
.ad r
9 channels at 230 \(*mW0 (\(em6.4 dBm0) each
2070 \(*mW0
.ad b
.RT
.ad r
2134\ \(*mW0
.ad b
.RT
.LP
.sp 2P
.LP
\fB2\fR \fBHigher order translating equipments\fR
.sp 1P
.RT
.sp 1P
.LP
2.1
\fIAllocation of loading\fR
.sp 9p
.RT
.PP
For the measurement of noise produced by higher order translating equipments
(groups, supergroups, etc. translating equipment), the values for
the allocation of the conventional load to the different translating equipments
are given in Table\ 1/G.222.
.PP
The number of incoherent band\(hylimited white noise signals is assumed
to be equal to the number of the input ports of the groups, supergroups,
etc. translating equipment under measurement. In certain circumstances,
however, the number of noise signals may be smaller than the number of
group input
ports.
.RT
.sp 1P
.LP
2.2
\fIMeasuring frequencies\fR
.sp 9p
.RT
.PP
The measuring frequencies in Table\ 1/G.230 are recommended.
.RT
.LP
.rs
.sp 15P
.ad r
\fBtable 1/G.230 (maintenu) T1.230, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
2.3
\fIFilter characteristics\fR
.sp 9p
.RT
.PP
The following filter characteristics are recommended:
.RT
.PP
2.3.1
bandpass filters (see Table 2/G.230);
.PP
2.3.2
bandstop filters (see Table 3/G.230).
.PP
\fINote\fR \ \(em\ Measuring frequencies of Table\ 1/G.230 and filter
characteristics of Tables\ 2/G.230 and 3/G.230 (with the exception of the
70\(hykHz filter) are the same as in CCIR Recommendations\ 399\ [1] and
482\ [2] and
CCITT Recommendation\ G.228 used for line system arrangements. Annex\ B to
Recommendation\ G.228 deals with the subject of corrections, if any, to be
applied to measurements to allow for filter effects.
.bp
.LP
.rs
.sp 22P
.ad r
\fBtable 2/G.230 (maintenu) T2.230, p.\fR
.sp 1P
.RT
.ad b
.RT
.ce
\fBH.T. [T3.230]\fR
.ce
TABLE\ 3/G.230
.ce
\fBBandstop filters\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(36p) | cw(30p) sw(36p) sw(30p) | cw(36p) sw(30p) | cw(30p) , ^ | c | c | c | c | c | ^ .
{
Centre
frequqency \fIf\fI
(kHz)
} {
Bandwith (kHz)
in relation to \fIf\fI
over
which the discrimination
should be at least
} {
Bandwith (kHz),
in relation to \fIf\fI
outside of
which the discrimination
should not exceed
} Notes
70 dB 55 dB 30 dB 3 dB 0.5 dB
_
.T&
cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | lw(30p) .
\ \ | 70 \(+-1.5 \(+-\ 1.7 \(+-\ 2.0 \(+-\ \ 5 \(+-\ 10
.T&
cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) .
\ \ | 98 \(+-1.5 \(+-\ 1.8 \(+-\ 2.1 \(+-\ \ 4 \(+-\ \ 9 a)
.T&
cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) .
\ \ | 31 \(+-1.5 \(+-\ 2.7 \(+-\ 4.0 \(+-\ 17 \(+-\ 30
.T&
cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) .
\ \ | 34 \(+-1.5 \(+-\ 3.5 \(+-\ 7.0 \(+-\ 15 \(+-\ 48 b)
.T&
cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) .
\ 1 | 02 \(+-1.5 \(+-\ 4.0 \(+-\ 9.0 \(+-\ 27 \(+-\ 90 a)
.T&
cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) .
\ 1 | 48 \(+-1.5 \(+-\ 4.0 \(+-11.0 \(+-\ 35 \(+-110 b)
.T&
cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) .
\ 1 | 30 \(+-1.5 \(+-\ 4.2 \(+-14.0 \(+-\ 48 \(+-155 a)
.T&
cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) .
\ 3 | 86 \(+-1.5 \(+-\ 1.8 \(+-\ 3.5 \(+-\ 12 \(+-100 b)
.T&
cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) .
\ 3 | 86 \(em \(+-15.0 \(+-30.0 \(+-110 \(+-350
.T&
cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) .
\ 9 | 73 \(+-1.5 \(+-\ 2.7 \(+-\ 5.8 \(+-\ 18 \(+-250
.T&
cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(36p) | cw(30p) | cw(30p) .
11 | 00 \(+-1.5 \(+-\ 3.0 \(+-\ 7.0 \(+-\ 20 \(+-300 b)
.TE
.LP
a)
CCIR Recommendation 482 [2].
.LP
b)
CCIR Recommendation 399 [1].
.TE
.nr PS 9
.RT
.ad r
\fBtable 3/G.230 [T3.230], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
2.4
\fIMeasuring procedures\fR
.sp 9p
.RT
.PP
The measuring procedures should comply with Recommendation\ G.228. Measurements
must be carried out with the regulators, if any, not included and with
the levels at the nominal value.
.PP
\fINote\fR \ \(em\ Some Administrations have chosen for groups and supergroups
not being tested in conformance with Table\ 1/G.230 higher values of the
load, but only for testing equipments with some margin to take account
of the
application where higher than nominal activity is to be expected.
.PP
As a consequence, in such cases, higher noise limits have to be
admitted than those indicated in Recommendation\ G.222, \(sc\ 4).
.bp
.RT
.sp 2P
.LP
\fB3\fR \fBThrough\(hyconnection filters\fR
.sp 1P
.RT
.sp 1P
.LP
3.1
\fIAllocation of loading\fR
.sp 9p
.RT
.PP
For the measurement of noise produced by through\(hyconnection filters
the values for the allocation of the conventional load according to
Table\ 2/G.223 to the different filters are given in Table\ 4/G.230.
.RT
.ce
\fBH.T. [T4.230]\fR
.ce
TABLE\ 4/G.230
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(60p) | cw(60p) | cw(60p) .
Filter for the basic {
Band of the noise
spectrum (kHz)
} {
Level of the noise power (dBm0)
}
_
.T&
lw(60p) | cw(60p) | cw(60p) .
Group {
\ | 12 to \ \ | 52
\ | 60 to \ \ | 08
} {
+ \ 6.1 (=^ \ | 60 channels)
+ \ 3.3 (=^ \ | 12 channels)
}
.T&
lw(60p) | cw(60p) | cw(60p) .
Supergroup {
\ | 60 to \ 1 | 96
\ | 16 to \ \ | 52
} {
+ \ 9.8 (=^ \ | 00 channels)
+ \ 6.1 (=^ \ | 60 channels)
}
.T&
lw(60p) | cw(60p) | cw(60p) .
Mastergroup \ | 16 to \ 2 | 00 {
+ 12.3 (=^ \ | 30 channels)
}
.T&
lw(60p) | cw(60p) | cw(60p) .
Supermastergroup 4 | 70 to 17 | 00 + 17.6 (=^ 1800 channels)
.T&
lw(60p) | cw(60p) | cw(60p) .
15 supergroup assembly \ | 16 to \ 8 | 60 + 17.6 (=^ 1800 channels)
.TE
.LP
\fINote\ 1\ \fR
\(em\ Group and supergroup through\(hyconnection filters require
two measurements. One with \*Qbroadband loading\*U with components outside
the pass\(hyband, and an additional one with loading in the passband only.
Since in these cases the number of transmitted channels is smaller than 240
(the range where the power level of the conventional load is not
proportional to 10\ log
1
0 | fIn\fR
, see \(sc\ 2.1 of Recommendation\ G.223)
the proportional part of the broadband loading transmitted in the passband
gives a loading which is lower than the conventional load for 12 or
60\ channels respectively.
.LP
\fINote\ 2\ \fR
\(em\ The choice of the correct load figure for the measurement of the
noise produced by the through\(hysupermastergroup filter requires careful
consideration bearing in mind that band limiting filters for a bandwidth
complying with actual load conditions are not available.
.nr PS 9
.RT
.ad r
\fBTable 4/G.230 [T4.230], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.2
\fIMeasuring frequencies\fR
.sp 9p
.RT
.PP
See \(sc\ 2.2.
.RT
.sp 1P
.LP
3.3
\fIFilter characteristics\fR
.sp 9p
.RT
.PP
Highpass and lowpass filters complying with Table\ 2/G.228 and\ [3] can
be used to limit the frequency of the noise spectrum. For bandstop filters,
see Table\ 3/G.230.
.RT
.sp 1P
.LP
3.4
\fIMeasuring procedures\fR
.sp 9p
.RT
.PP
The measuring procedure should comply with Recommendation\ G.228. For through\(hygroup
and through\(hysupergroup filters, two measurements have to be carried
out in the appropriate measuring slots in the passband.
.RT
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCIR Recommendation \fIMeasurement of noise using a continuous uniform\fR
\fIspectrum signal on frequency\(hydivision multiplex telephony\fR \fIradio\(hyrelay
systems\fR , Vol.\ IX, Rec.\ 399, Dubrovnik,\ 1986.
.LP
[2]
CCIR Recommendation \fIMeasurement of performance by means of a signal
of\fR \fIa uniform spectrum for systems using frequency\(hydivision multiplex\fR
\fItelephony in the fixed satellite service\fR , Vol.\ IV, Rec.\ 482,
Dubrovnik,\ 1986.
.LP
[3]
CCIR Recommendation \fIMeasurement of performance by means of a signal\fR
\fIof a uniform spectrum for systems using frequency\(hydivision multiplex\fR
\fItelephony in the fixed satellite service\fR , Vol.\ IV, Rec.\ 482,
Table\ I, Dubrovnik,\ 1986.
.LP
.bp