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InfoMagic Standards 1994 January
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InfoMagic Standards - January 1994.iso
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ccitt
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1988
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.rs
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.\" Not Copyright (~c) 1991
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.EN
.nr LL 40.5P
.nr ll 40.5P
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.rs
\v'|.5i'
.sp 1P
.ce 1000
\v'12P'
\s12FASCICLE\ VIII.1
\v'4P'
.RT
.ce 0
.sp 1P
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\fBSeries V Recommendations\fR \v'2P'
.EF '% \ \ \ ^''
.OF ''' \ \ \ ^ %'
.ce 0
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\fBDATA\ COMMUNICATION\fR
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\fBOVER\ THE\ TELEPHONE\ NETWORK
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.LP
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.EF '% \ \ \ ^''
.OF ''' \ \ \ ^ %'
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.RT
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.bp
.LP
\fBMONTAGE:\fR \ PAGE 2 = PAGE BLANCHE
.sp 1P
.RT
.LP
.bp
.ce 1000
\v'4P'
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PRINCIPLES\ GOVERNING\ THE\ COLLABORATION\ BETWEEN\ THE\ CCITT
.sp 1P
.RT
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AND\ OTHER\ INTERNATIONAL\ ORGANIZATIONS\ IN\ THE\ STUDY
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OF\ DATA\ COMMUNICATIONS
\v'6p'
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Recommendation A.20 published in Volume\ I is reproduced below for the
convenience
.sp 1P
.RT
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of the reader of the Series\ V Recommendations.
\v'2P'
.ce 0
.sp 1P
.sp 2P
.LP
\fBRecommendation\ A.20\fR
.RT
.sp 2P
.ce 1000
\fBCOLLABORATION\ WITH\ OTHER\ INTERNATIONAL\ ORGANIZATIONS\fR
.EF '% Fascicle\ VIII.1\ \(em\ Rec.\ A.20''
.OF '''Fascicle\ VIII.1\ \(em\ Rec.\ A.20 %'
.ce 0
.sp 1P
.ce 1000
\fBOVER\ DATA\ TRANSMISSION\fR
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1964; amended at Mar del Plata, 1968, and at Geneva, 1972,\fR
.sp 9p
.RT
.ce 0
.sp 1P
.ce 1000
\fI1976 and 1980; Malaga\(hyTorremolinos, 1984)\fR \v'6p'
.ce 0
.sp 1P
.sp 2P
.LP
The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR
.sp 9p
.RT
.PP
(a)
that, according to Article 1 of the agreement between the United Nations
and the International Telecommunication Union, the United
Nations recognizes the International Telecommunication Union as the specialized
agency responsible for taking such action as may be appropriate under its
basic instrument for the accomplishment of the purposes set forth therein;
.PP
(b)
that Article 4 of the International Telecommunication
Convention (Nairobi, 1982) states that the purposes of the Union are:
.LP
\*Qa)
to maintain and extend international cooperation between
all Members of the Union for the improvement and rational use of
telecommunications of all kinds, as well as to promote and to
offer technical assistance to developing countries in the field
of telecommunications;
.LP
b)
to promote the development of technical facilities and
their most efficient operation with a view to improving the
efficiency of telecommunication services, increasing their
usefulness and making them, so far as possible, generally
available to the public;
.LP
c)
to harmonize the actions of nations in the attainment
of those ends;\*U
.PP
(c)
that Article 40 of the Convention states that, in
furtherance of complete international coordination on matters affecting
telecommunication, the Union shall cooperate with international organizations
having related interests and activities;
.PP
(d)
that in the study of data transmission the CCITT has to
collaborate with the organizations dealing with data processing and office
equipment and particularly the International Organization for Standardization
(ISO) and the International Electrotechnical Commission\ (IEC);
.PP
(e)
that this collaboration has to be organized in a manner
that will avoid duplication of work and decisions that would be contrary
to the principles set out above;
.bp
.sp 1P
.LP
\fIunanimously declares the view\fR
.sp 9p
.RT
.PP
that international standards for data transmission should be
established with the following considerations in mind:
.PP
(1)
Clearly it will be the responsibility of the CCITT to lay down standards
for \fItransmission channels\fR , i.e.\ aspects of data
transmission which require a knowledge of telecommunication networks or
affect performance of these networks.
.PP
(2)
The standardization of signal conversion terminal equipment (modems) is
the province of the CCITT; the standardization of the junction
(interface) between modem and the data terminal equipment is a matter of
agreement between the CCITT and the ISO or the\ IEC.
.PP
(3)
Devices designed to detect and (or) correct errors must
take account of:
.LP
\(em
the error rate tolerable to the user;
.LP
\(em
the line transmission conditions;
.LP
\(em
the code, which has to meet the exigencies of the data
alphabet and the requirements of error control (this must be
such as to give an output satisfactory to the user) together
with the requisite signalling (synchronism, repetition
signals,\ etc.).
.PP
Standardization here may not come wholly within the CCITT's
province, but the CCITT has very considerable interests at stake.
.PP
(4)
The alphabet (as defined in Fascicle X.1\ \(em\ Terms and
Definitions) is a \*Qtable of correspondence between an agreed set of characters
and the signals which represent them\*U.
.PP
The CCITT and the ISO reached agreement on an alphabet for general (but
not exclusive) use for data and message transmission and have standardized
a common alphabet which is known as International Alphabet\ No.\ 5 (CCITT
Recommendation\ T.50 and ISO Standard\ No.\ 646\(hy1983; ISO\ 7\(hybit
coded character
set for information interchange).
.PP
Complementary study of some control characters of the alphabet
should be effected cooperatively.
.RT
.PP
(5)
Coding (as defined in Fascicle X.1\ \(em\ Terms and
Definitions) is \*Qa system of rules and conventions according to which the
telegraph signals forming a message or the data signals forming a block
should be formed, transmitted, received and processed\*U. Hence, it consists
of a
transformation of the format of the signals in the alphabet for taking
account of synchronous methods, and introduction of redundancy in accordance
with the error control system. This is not a field in which the CCITT alone
may be able to decide; however, no decision should be taken without reference
to the
Committee, because of the possible restrictions which transmission and
switching peculiarities may impose on coding.
.PP
When the general switched network is used (telephone or telex) and when
the error control devices are subject to restrictions (switching signals\
\(em reserved sequences), it is the CCITT which is in fact responsible
for any
necessary standardization in conjunction with other bodies.
.PP
(6)
The limits to be observed for transmission performance on the transmission
path (modem included) fall within the competence of the CCITT; the limits
for the transmission performance of the sending equipment and the
margin of terminal data equipment (depending on the terminal apparatus
and the transmission path limits) should be fixed by agreement between
the ISO and the CCITT.
.PP
(7)
In all instances, the CCITT alone can lay down manual and automatic operating
procedures for the setting\(hyup, holding and clearing of
calls for data communications when the general switched networks are used,
including type and form of signals to be interchanged at the interface
between data terminal equipment and data circuit terminating
equipment.
.PP
(8)
When a public data network is involved, the CCITT has the responsibility
to provide the Recommendations which apply. Where these
Recommendations have an impact on the basic design and features of data
processing systems and office equipment [normally the Data Terminal Equipment
(DTE)], they shall be the subject of consultation between CCITT and ISO
and in some cases a mutual agreement may be desirable. Likewise when the
ISO is
developing or changing standards that may affect compatibility with the
public data network there shall be consultation with the CCITT.
.LP
.bp
.sp 1P
.ce 1000
\v'3P'
SECTION\ 1
.ce 0
.sp 1P
.ce 1000
\fBGENERAL\fR \v'6p'
.ce 0
.sp 1P
.sp 2P
.LP
\fBRecommendation\ V.1\fR
.RT
.sp 2P
.ce 1000
\fBEQUIVALENCE\ BETWEEN\ BINARY\ NOTATION\ SYMBOLS\fR
.EF '% Fascicle\ VIII.1\ \(em\ Rec.\ V.1''
.OF '''Fascicle\ VIII.1\ \(em\ Rec.\ V.1 %'
.ce 0
.sp 1P
.ce 1000
\fBAND\ THE\ SIGNIFICANT\ CONDITIONS\ OF\ A\ TWO\(hyCONDITION\ CODE\fR
.ce 0
.sp 1P
.ce 1000
\fI(New Delhi, 1960; amended at Geneva, 1964 and 1972)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.PP
Binary numbering
expresses numbers by means of two
digits normally represented by the symbols\ 0 and\ 1. Transmission channels
are especially well suited to the transmission of signals by a modulation
having two significant conditions (two\(hycondition modulation). These two
significant conditions are sometimes called \*Qspace\*U and \*Qmark\*U
or \*Qstart\*U and \*Qstop\*U, or they may be called condition\ A or condition\
Z\ [1].
.sp 1P
.RT
.PP
It is very useful to make the two conditions of a two\(hycondition
modulation correspond to the binary digits\ 0 and\ 1. Such equivalence will
facilitate the transmission of numbers resulting from binary calculation,
the conversion of codes for binary numbers and of codes for decimal numbers,
maintenance operations and relations between transmission personnel and the
personnel in charge of data\(hyprocessing machines.
.PP
At first sight, it does not seem to matter whether the symbol\ 0
corresponds in transmission to condition\ A or condition\ Z, the symbol\ 1 then
corresponding to condition\ Z or condition\ A or vice versa.
.PP
In telegraphy, however, when a telegraphic communication is set up and
the sending of signals is stopped (called the idle condition of the line),
the signal sent over the line consists of condition\ Z throughout the suspension
of transmission.
.PP
It is logical (and for certain\ VF telegraph systems also essential) to
use the same rule in data transmission. During the \*Qidle periods\*U of
transmission, condition\ Z should be applied to the circuit input.
.PP
Data transmission on a circuit is often controlled by perforated tape.
On perforated tapes used for telegraphy, condition\ Z is represented by
perforation. When binary numbers are represented by means of perforations,
it is customary to represent the symbol\ 1 by a perforation. It is therefore
logical to make this symbol\ 1 correspond to condition\ Z.
.RT
.LP
For these reasons, the CCITT
.sp 1P
.RT
.sp 2P
.LP
\fIunanimously declares the following view:\fR
.sp 1P
.RT
.PP
\fB1\fR In transmitting data by two\(hycondition code, in which the
digits are formed using binary notation, the symbol\ 1 of the binary notation
will be equivalent to condition\ Z of the modulation, and the symbol\ 0 of the
binary notation will be equivalent to condition\ A of the modulation.
.sp 9p
.RT
.PP
\fB2\fR During periods when there is no signal sent to the input of the
circuit, the circuit input condition is condition\ Z.
.bp
.sp 9p
.RT
.PP
\fB3\fR If
perforation
is used, one perforation corresponds to
one unit interval under condition\ Z.
.sp 9p
.RT
.PP
\fB4\fR In accordance with Recommendation\ R.31, the sending of symbol\ 1
(condition\ Z) corresponds to the tone being sent on a channel using amplitude
modulation.
.sp 9p
.RT
.PP
\fB5\fR
In accordance with Recommendation\ R.35, when frequency
modulation is used, the sending of symbol\ 0 corresponds to the higher
frequency, while the sending of symbol\ 1 corresponds to the lower
frequency.
.sp 9p
.RT
.sp 1P
.LP
\fB6\fR a)
For
phase modulation
with reference phase:
.sp 9p
.RT
.LP
the symbol\ 1 corresponds to a phase equal to the
reference phase;
.LP
the symbol\ 0 corresponds to a phase opposed to the
reference phase.
.LP
b)
For
differential two\(hyphase modulation
where the
alternative phase changes are 0\ degree or
180\ degrees:
.LP
the symbol\ 1 corresponds to a phase inversion from
the previous element;
.LP
the symbol\ 0 corresponds to a no\(hyphase inversion from
the previous element.
.PP
\fB7\fR
A summary of equivalence is shown in Table\ 1/V.1.
.sp 9p
.RT
.ce
\fBH.T. [T1.10]\fR
.ce
TABLE\ 1/V.10
.ce
\fBReceiver significant levels\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(48p) .
T{
\fIV\fR
A
` \(em \fIV\fR
B
` \(= \(em0.3 V
T} T{
\fIV\fR
A
` \(em \fIV\fR
B
` \(>=" +0.3 V
T}
.T&
lw(84p) | cw(48p) | cw(48p) .
Data circuits 1 0
_
.T&
lw(84p) | cw(48p) | cw(48p) .
Control and timing circuits OFF ON
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 1/V.1, [T1.1], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
.sp 1
\fBReference\fR
.sp 1P
.RT
.LP
[1]
CCITT Definition: \fIPosition A; position Z\fR , Vol. X,
(Terms and Definitions).
.bp
.sp 2P
.LP
\fBRecommendation\ V.2\fR
.FS
Recommendation V.2 corresponds to
Recommendation\ H.15 [1].
.FE
.RT
.sp 2P
.sp 1P
.ce 1000
\fBPOWER\ LEVELS\ FOR\ DATA\ TRANSMISSION\ OVER\ TELEPHONE\ LINES\fR
.EF '% Fascicle\ VIII.1\ \(em\ Rec.\ V.2''
.OF '''Fascicle\ VIII.1\ \(em\ Rec.\ V.2 %'
.ce 0
.sp 1P
.ce 1000
\fI(New Delhi, 1960; amended at Geneva, 1964 and 1980)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.PP
The objectives in specifying
data signal levels
are as
follows:
.sp 1P
.RT
.LP
a)
To ensure satisfactory transmission and to permit
coordination with devices such as signalling receivers or echo
suppressors, the data signal levels on international circuits
should be controlled as closely as possible,
.LP
b)
To ensure correct performance of
multichannel carrier
systems
from the point of view of loading and noise, the mean
power of
data circuits
should not differ much from the
conventional value of channel loading (\(em15\ dBm0 for each
direction of transmission: see Note below). This conventional
value makes allowance for a reasonable proportion\ P (dependent
on the transmission systems and probably less than\ 50%; the
value will have to be specified in subsequent studies) of the
channels in a multichannel system being used for nonspeech
applications at fixed power levels at about \(em13\ dBm0 for each
direction of transmission.
.LP
If the proportion of nonspeech applications (including data) does not
exceed the above value\ P, the mean power of \(em13\ dBm0
for each direction of transmission would be allowable for data
transmission also.
.LP
However, assuming that the proportion of nonspeech circuits is appreciably
higher than\ P (due to the development of data
transmission) on international carrier systems, a reduction of
this power by\ 2\ dB might be reasonable (these values require
further study).
.LP
\fINote\fR \ \(em\ The distribution of long\(hyterm mean power among
the channels in a multichannel carrier telephone system
(conventional mean value of \(em15\ dBm0), probably has a standard
deviation in the neighbourhood of 4\ dB (see\ [2]).
.LP
c)
It is probable that Administrations will wish to fix
specific values for the signal power level of data modulators
either at the subscriber's line terminals or at the local
exchanges. The relation between these values and the power
levels on international circuits depends on the particular
national transmission plan; in any case, a wide range of losses
among the possible connections between the subscriber and the
input to international circuits must be expected.
.LP
d)
Considerations\ a) to\ c) suggest that specification of the
maximum data signal level only is not the most useful form. One
alternative proposal would be to specify the nominal power at
the input to the international circuit. The nominal power would
be the statistically estimated mean power obtained from
measurement on many data transmission circuits.
.LP
For these reasons, the CCITT
.sp 1P
.RT
.sp 2P
.LP
\fIunanimously declares the following view:\fR
.sp 1P
.RT
.sp 1P
.LP
\fB1\fR \fBData transmission over leased telephone circuits\fR
\fB(private wires) set up on carrier systems\fR
.sp 9p
.RT
.PP
1.1
The maximum power output of the subscriber's equipment
into the line shall not exceed 1\ mW at any frequency.
.sp 9p
.RT
.PP
1.2
For systems transmitting tones continuously, e.g.,
frequency\(hymodulation systems, the maximum power level at the zero relative
level point shall be \(em13\ dBm0. When transmission of data is discontinued
for
any appreciable time, the power level should preferably be reduced to \(em20\
dBm0 or lower.
.bp
.sp 9p
.RT
.PP
1.3
For systems not transmitting tones continuously, e.g.,
amplitude\(hymodulation systems, the signal characteristics should meet
all of the following requirements:
.sp 9p
.RT
.LP
i)
The maximum value of the 1\(hyminute mean power shall not
exceed \(em13\ dBm0.
.LP
ii)
Provisionally, the maximum value of the instantaneous power shall not
exceed a level corresponding to that of a 0\ dBm0
sine wave signal. This limit should be confirmed or amended after
further study.
.LP
iii)
Provisionally, the maximum signal power determined for a 10\(hyHz\ bandwidth
centred at any frequency shall not exceed
\(em10\ dBm0. This limit should be confirmed or amended after
further study.
.PP
\fINote\ 1\fR \ \(em\ It is estimated that the proportion of international
circuits which are carrying data transmissions is approximately\ 20%. If the
proportion should reach a high level (approximately\ 50% or even less in the
case of high\(hyusage systems), the limits now proposed would need to be
reconsidered.
.PP
\fINote\ 2\fR \ \(em\ Supplement No.\ 16 [3] of the Yellow Book, Volume\
III, gives information on the out\(hyof\(hyband power of signals applied
to leased
telephone\(hytype circuits.
.RT
.sp 2P
.LP
\fB2\fR \fBData transmission over the switched telephone
system\fR
.sp 1P
.RT
.PP
2.1
The maximum power output of the subscriber's equipment into
the line shall not exceed 1\ mW at any frequency.
.sp 9p
.RT
.PP
2.2
For systems transmitting tones continuously, such as frequency\(hy or phase\(hymodulation
systems, the power level of the subscriber's equipment
should be fixed at the time of installation to allow for loss between his
equipment and the point of entry to an international circuit, so that the
corresponding nominal level of the signal at the international circuit input
shall not exceed \(em13\ dBm0.
.sp 9p
.RT
.PP
2.3
For systems not transmitting tones continously, e.g.
amplitude\(hymodulation systems, the signal characteristics should meet
all of the following requirements (see also Note\ 1 to \(sc\ 1.3):
.sp 9p
.RT
.LP
i)
The maximum value of the 1\(hyminute mean power shall not
exceed\ \(em13\ dBm0.
.LP
ii)
Provisionally, the maximum value of the instantaneous power shall not
exceed a level corresponding to that of a 0\ dBm0
sine wave signal. This limit should be confirmed or amended
after further study.
.LP
iii)
Provisionally, the maximum signal power determined for a 10\ Hz bandwidth
centred at any frequency shall not exceed
\(em10\ dBm0. This limit should be confirmed or amended after
further study.
.PP
\fINote\ 1\fR \ \(em\ In practice, it is no easy matter to assess the loss
between a subscriber's equipment and the international circuit, so that \(sc\ 2
of the present Recommendation should be taken as providing general planning
guidance.
.PP
\fINote\ 2\fR \ \(em\ In switched connections, the loss between subscribers'
telephones may be high: 30\ to\ 40\ dB. The level of the signals received will
then be very low, and these signals may suffer disturbance from the dialling
pulses sent over other circuits.
.PP
If there is likely to be a heavy demand for international connections for
data transmission over the switched network, some Administrations might
want to provide special 4\(hywire subscriber lines. If so, the levels to
be used might be those proposed for leased circuits.
.RT
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fIPower levels for data transmission over telephone\fR
\fIlines\fR , Vol.\ III, Rec.\ H.51.
.LP
[2]
\fIMeasurement of the load of telephone circuits\fR , Green Book, Vol.\
III\(hy2, Supplement No.\ 5, ITU, Geneva,\ 1973.
.LP
[3]
\fIOut\(hyof\(hyband characteristics of signals applied to leased\fR
\fItelephone\(hytype circuits\fR , Vol.\ III, Supplement\ No.\ 16.
.bp
.sp 2P
.LP
\fBRecommendation\ V.4\fR
.RT
.sp 2P
.ce 1000
\fBGENERAL\ STRUCTURE\ OF\ \fR \fBSIGNALS\ OF\|\fR \fBINTERNATIONAL\ ALPHABET\
No.\ 5\ CODE\fR
.EF '% Fascicle\ VIII.1\ \(em\ Rec.\ V.4''
.OF '''Fascicle\ VIII.1\ \(em\ Rec.\ V.4 %'
.ce 0
.sp 1P
.ce 1000
\fBFOR\ CHARACTER\ ORIENTED\ DATA\ TRANSMISSION\ OVER\ PUBLIC\ TELEPHONE\|
NETWORKS\fR
.FS
See Recommendation\ X.4\ [1] for data transmission over
public data networks.
.FE
.ce 0
.sp 1P
.ce 1000
\fI(Mar del Plata, 1968; amended at Geneva, 1976 and 1980, and at\fR
\fIMelbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
I.
\fIconsidering, firstly,\fR
.sp 9p
.RT
.PP
the agreement between the International Organization for\fR
Standardization (ISO) and the CCITT on the main characteristics of a
seven\(hyunit alphabet [International Alphabet\ No.\ 5 (IA5)] to be used
for data transmission and for telecommunications requirements that cannot
be met by the existing five\(hyunit International Telegraph Alphabet\ No.\
2 (ITA2);
.PP
the interest, both to the users and to the telecommunication services,
of an agreement concerning the chronological order of transmission of bits
in serial working;
.RT
.sp 1P
.LP
\fIdeclares the view\fR
.sp 9p
.RT
.PP
that the agreed rank number of the unit in the alphabetical table of combinations
should correspond to the chronological order of transmission in serial
working on telecommunication circuits;
.PP
that, when this rank in the combination represents the order of the
bit in binary numbering, the bits should be transmitted in serial working
with the low order bit first;
.PP
that the numerical meaning corresponding to each information unit
considered in isolation is that of the digit:
.PP
0 for a unit corresponding to condition\ A (travail\ =\ space), and
.PP
1 for a unit corresponding to condition\ Z (repos\ =\ mark),
.RT
.LP
in accordance with the definitions of these conditions for a two\(hycondition
transmission system;
.sp 1P
.LP
II.
\fIconsidering, moreover,\fR
.sp 9p
.RT
.PP
that it is often desirable, in character oriented data
transmission, to add an extra \*Qparity\*U unit to allow for the detection of
errors in received signals;
.PP
the possibility offered by this addition for the detection of faults in
data terminal equipment;
.PP
the need to reserve the possibility of making this addition during the
transmission itself, after the seven information units proper have been
sent;
.RT
.sp 1P
.LP
\fIdeclares the view\fR
.sp 9p
.RT
.PP
that signals of the International Alphabet\ No.\ 5 code for data
transmission should, in general, include an additional \*Qparity\*U unit;
.PP
that the rank of this unit and, hence, the chronological order of the transmission
in serial working should be the eighth of the combination thus
completed;
.RT
.sp 1P
.LP
III.
\fIconsidering\fR
.sp 9p
.RT
.PP
that, in
start\(hystop systems
working with electromechanical equipment, the margin of such equipment
and the reliability of the connection are considerably increased by the
use of a stop element corresponding to the
duration of two unit intervals of the modulation;
.PP
that for transmissions over telephone circuits via modems installed on
the user's premises, the latter must be able to use the connections at
the
highest possible practical rate in characters per second, and that in such a
case a single\(hyunit stop element leads to a gain of about 10% as regards
this practical rate;
.bp
.PP
that, however, it does not appear that the production of electronic
devices capable of working at will with start\(hystop signals having a stop
element equal to one or two unit intervals should lead to costly complications
and that such an arrangement can have the advantage of appreciably limiting
the error rate without greatly reducing the practical efficiency of the
connection;
.RT
.sp 1P
.LP
\fIdeclares the view\fR
.sp 9p
.RT
.PP
that in start\(hystop systems using combinations of the seven\(hyunit
alphabet normally followed by a parity unit, the first information unit
of the transmitted combination should be preceded by a start element corresponding
to condition\ A (space);
.PP
that the duration of this start element should be a one\(hyunit interval
for the modulation rate under consideration, at transmitter output;
.PP
that the combination of seven information units, normally completed by
its parity unit, should be followed by a stop element corresponding to
condition\ Z (mark);
.PP
that for start\(hystop systems using the seven\(hyunit code on switched
telephone networks, a two\(hyunit stop element should be used with
electromechanical data terminal equipments operating at modulation rates
up to and including 200\ bauds. In other cases, the use of a one\(hyunit
stop element is preferable. However, this is subject to a mutual agreement
between
Administrations concerned;
.PP
that similar situations when a one\(hyunit stop element can be used may
apply to leased circuits;
.PP
that the
start\(hystop receivers
should be capable of correctly receiving start\(hystop signals comprising
a single\(hyunit stop element, whose
duration will be reduced by a time interval equal to the deviation
corresponding to the degree of gross start\(hystop distortion permitted at
receiver input.\fR However, for electromechanical equipment which must use a
two\(hyunit stop element (eleven\(hyunit code signal) with a modulation rate of
200\ bauds or less, receivers should be capable of correctly receiving
signals with a stop element reduced to one unit;
.RT
.sp 1P
.LP
IV.
\fIconsidering, finally,\fR
.sp 9p
.RT
.PP
that the direction of the
parity unit
can only be that of the
even parity
on the perforated tapes, particularly owing to the
possibility of deletion (combination\ 7/15 of the alphabet) which causes
a hole to appear in all tracks;
.PP
that, on the other hand, the
odd parity
is considered
essential in the equipment which depends on transitions in the signals to
maintain synchronism [in cases where combination\ 1/6 (SYNC) of the alphabet
does not permit of an economical solution];
.RT
.sp 1P
.LP
\fIdeclares the view\fR
.sp 9p
.RT
.PP
that the parity unit of the signal should correspond to the even
parity in links or connections operated on the principle of the start\(hystop
system;
.PP
that this parity should be odd on links or connections using
end\(hyto\(hyend character oriented synchronous operation;
.PP
that arrangements should be made when necessary to reverse the
direction of the parity unit at the input and output of the synchronous
equipment connected either to apparatus working on the start\(hystop principle
or receiving characters on perforated tape;
.PP
that the detection of a character out\(hyof\(hyparity may be represented
by:
.RT
.LP
a)
reverse question mark
(\ ) graphic character or a
representation of the capital letters SB (see ISO\ 2047) provided
that these letters occupy a single character position on the
screen or printer, and could have been entered by a single key
stroke, recognizing it may be difficult to achieve a legible \*QSB\*U
character from some matrix printers or displays where
the characters are printed; or
.LP
b)
a recording of the 1/10 (SUB) character on the tape or other storage
medium, where provided
.PP
and that, where a SUB character occurs in a received transmission, or is
presented to a DTE via a storage medium, e.g.\ paper tape, then the
reaction should be as in\ a) and\ b) above.
.sp 2P
.LP
\fBReference\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fIGeneral structure of signals of International\fR
\fIAlphabet No.\ 5 code for character oriented data transmission over public
data\fR \fInetworks\fR , Vol.\ VIII, Rec.\ X.4.
.bp
.sp 2P
.LP
\fBRecommendation\ V.5\fR
.RT
.sp 2P
.ce 1000
\fBSTANDARDIZATION\ OF\ \fR \fBDATA\ SIGNALLING\ RATES\ FOR\fR
.EF '% Fascicle\ VIII.1\ \(em\ Rec.\ V.5''
.OF '''Fascicle\ VIII.1\ \(em\ Rec.\ V.5 %'
.ce 0
.ce 1000
\fBSYNCHRONOUS\ DATA\ TRANSMISSION\fR
.ce 0
.sp 1P
.ce 1000
\fBIN\ THE\ GENERAL\ SWITCHED\ TELEPHONE\ NETWORK\fR
.ce 0
.sp 1P
.ce 1000
\fI(former Recommendation\ V.22, Geneva, 1964;\fR
.sp 9p
.RT
.ce 0
.ce 1000
\fIamended at Mar del Plata, 1968, at Geneva, 1972 and 1976,\fR
.ce 0
.sp 1P
.ce 1000
\fIat Malaga\(hyTorremolinos, 1984 and at Melbourne, 1988)\fR
.ce 0
.sp 1P
.PP
\fB1\fR Data transmission by international communications carried on
the general switched telephone network using a synchronous transmission
procedure will be done with a specific mode of modulation, two\(hy or
multi\(hycondition, and serial transmission (see Note\ 1). For synchronous data
transmission on leased telephone\(hytype circuits see Recommendation\ V.6.
.sp 1P
.RT
.PP
\fB2\fR The data signalling rates for synchronous transmission in the
general switched telephone network will be:
.sp 9p
.RT
.sp 1P
.ce 1000
600, 1200, 2400, 4800 and 9600 bits (see Note\ 2).
.ce 0
.sp 1P
.LP
The users will choose among these rates, in accordance with their needs
and the facilities afforded by the connection.
.PP
\fB3\fR Data signalling rates should in no case deviate from the
nominal value by more than \(+-\|0.01%.
.sp 9p
.RT
.PP
\fINote\ 1\fR \ \(em\ The application of parallel data transmission is a
subject of other Recommendations.
.PP
\fINote\ 2\fR \ \(em\ Modems for use in the general switched telephone
network at these data signalling rates; see Recommendations\ V.23, V.26\|\fIbis\fR
and V.27\|\fIter\fR respectively for a half\(hyduplex mode of operation,
and V.22,
V.22\|\fIbis\fR , V.26\|\fIter\fR and V.32, respectively, for a duplex\(hymode
of
operation.
.PP
\fINote\ 3\fR \ \(em\ For asynchronous data transmission at 300\ bit/s, see
Recommendation\ V.21.
.RT
.sp 2P
.LP
\fBRecommendation\ V.6\fR
.RT
.sp 2P
.ce 1000
\fBSTANDARDIZATION\ OF\ \fR \fBDATA\ SIGNALLING\ RATES\ FOR\fR
.EF '% Fascicle\ VIII.1\ \(em\ Rec.\ V.6''
.OF '''Fascicle\ VIII.1\ \(em\ Rec.\ V.6 %'
.ce 0
.sp 1P
.ce 1000
\fBSYNCHRONOUS\ DATA\ TRANSMISSION\ ON\ LEASED\ TELEPHONE\(hyTYPE\ CIRCUITS\fR
.ce 0
.sp 1P
.ce 1000
\fI(former Recommendation\ V.22\|bis, Geneva, 1972;\fR
.sp 9p
.RT
.ce 0
.sp 1P
.ce 1000
\fIamended at Geneva, 1976, at Malaga\(hyTorremolinos, 1984 and at\fR
\fIMelbourne, 1988)\fR
.ce 0
.sp 1P
.PP
\fB1\fR Data transmission by international communications carried on
leased telephone\(hytype circuits (either normal quality or special quality
circuits) using a synchronous transmission procedure will be done with a
specific mode of modulation, two\(hy or multi\(hycondition, and serial
transmission (see Note\ 1). For synchronous data transmission in the general
switched telephone network see Recommendation\ V.5.
.sp 1P
.RT
.PP
\fB2\fR
It is recommended that for synchronous transmission the data
signalling rates should be divided into two distinct classes to be known as
\*Qpreferred\*U and \*Qsupplementary\*U, both of which are included in
the \*Qpermitted\*U data signalling rates.
.sp 9p
.RT
.sp 1P
.LP
a)
\fIPreferred range of data signalling rates\fR
\fI(bits per second)\fR
.sp 9p
.RT
.LP
\ \|600\ (see\ Note\ 2)
\ 4\|800 (see Note\ 2)
.LP
1\|200\ (see\ Note\ 2)
\ 9\|600 (see Note\ 2)
.LP
2\|400\ (see\ Note\ 2)
14\|400 (see Note\ 2)
.LP
b)
\fISupplementary range of data signalling rates\fR
\fI(bits per second)\fR
.LP
3\|000 (see Note 3)
\ 7\|200 (see Note 2)
.LP
6\|000 (see Note 3)
12\|000 (see Note 3)
.LP
c)
\fIPermitted range of data signalling rates\fR
\fI(bits per second)\fR
.LP
The range is defined as 600\ times \*Q\fIN\fR \*U bits per
second where 1\ \(=\ \fIN\fR \ \(=\ 24;\ \fIN\fR : a positive integer.
.bp
.PP
In determining the permitted range, the CCITT has in mind the need to restrict
the number of data signalling rates (and hence modem design
required), yet at the same time to allow the best use to be made of technical
progress in both modem development and improvement in the telephone plant.
It is considered that a geometric progression in standard rates provides
the most satisfactory basis of development.
.PP
\fB3\fR
Data signalling rates should in no case deviate from the
nominal value by more than \(+-\|0.01%.
.sp 9p
.RT
.PP
\fINote\ 1\fR \ \(em\ The application of parallel data transmission is a
subject of other Recommendations.
.PP
\fINote\ 2\fR \ \(em\ Modems for use on leased telephone\(hytype circuits
at these
data signalling rates; see Recommendations\ V.22, V.22\|\fIbis\fR , V.23, V.26,
V.26\|\fIter\fR , V.27, V.27\|\fIbis\fR , V.29, V.32 and V.33.
.PP
\fINote\ 3\fR \ \(em\ It is recognized that there is a usage of these data
signalling rates for the connection of DTEs to
circuit switched public data networks
. Addition of other data signalling rates for this purpose is under consideration.
.PP
\fINote\ 4\fR \ \(em\ Modems for use on leased telephone\(hytype circuits
at these signalling rates are under study.
\v'6p'
.RT
.sp 2P
.LP
\fBRecommendation\ V.7\fR
.RT
.sp 2P
.ce 1000
\fBDEFINITIONS\ OF\ TERMS\ CONCERNING\ DATA\ COMMUNICATION\fR
.EF '% Fascicle\ VIII.1\ \(em\ Rec.\ V.7''
.OF '''Fascicle\ VIII.1\ \(em\ Rec.\ V.7 %'
.ce 0
.sp 1P
.ce 1000
\fBOVER\ THE\ TELEPHONE\ NETWORK\fR
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1980; amended at Malaga\(hyTorremolinos, 1984\fR \fIand at
Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.PP
\fINote\fR \ \(em\ This Recommendation contains only new and amended
definitions of terms concerning data communication over the telephone network
which were elaborated by Study Group\ XVII since 1977 and approved by the
VIIth and VIIIth Plenary Assemblies of the CCITT.
.sp 1P
.RT
.PP
It should be noted that there exist a large number of relevant
definitions in force which have been published in the \fIList of definitions
of\fR \fIessential telecommunication terms\fR , Part\ I (including its
two Supplements),
\fIGreen Book\fR , Volume\ VIII and \fIOrange Book\fR , Volume\ VIII.2.
.sp 2P
.LP
\fB1\fR \fBeffective data transfer rate\fR
.sp 1P
.RT
.LP
\fIF:\ d\*'ebit effectif du transfert des donn\*'ees\fR
.LP
\fIS:\ velocidad real de transferencia de datos\fR
.PP
The average number of bits, characters, or blocks per unit time
transferred from a data source to a data sink and accepted as valid. It is
expressed in bits, characters, or blocks per second, minute, or hour.
.RT
.sp 2P
.LP
\fB2\fR \fBerror control\fR
.sp 1P
.RT
.LP
\fIF:\ contr\*\|ole des erreurs\fR
.LP
\fIS:\ control de errores\fR \|(protecci\*'on contra errores)
.PP
That part of a protocol controlling the detection and possibly the correction
of transmission errors.
.RT
.sp 2P
.LP
\fB3\fR \fBdata concentrator\fR
.sp 1P
.RT
.LP
\fIF:\ concentrateur de donn\*'ees\fR
.LP
\fIS:\ concentrador de datos\fR
.PP
Equipment that permits a common transmission medium to serve more \fIdata
sources\fR than there are data channels currently available within the
transmission medium.
.bp
.RT
.sp 2P
.LP
\fB4\fR \fBsimple multipoint circuit\fR
.sp 1P
.RT
.LP
\fIF:\ circuit multipoint simple\fR
.LP
\fIS:\ circuito multipunto simple\fR
.PP
A multipoint circuit that does not contain more than two DCEs in series
and that provides for centralized multipoint operation.
.RT
.sp 2P
.LP
\fB5\fR \fBinband signalling\fR
.sp 1P
.RT
.LP
\fIF:\ signalisation dans la bande\fR
.LP
\fIS:\ se\o"n~"alizaci\*'on dentro de banda\fR
.PP
The exchange of control signals between interconnected DCEs using the DCE
line signal band with which data in the forward channel are
transmitted. The transmission of DTE data, if any, is disrupted.
.RT
.sp 2P
.LP
\fB6\fR \fBout\(hyof\(hyband signalling\fR
.sp 1P
.RT
.LP
\fIF:\ signalisation hors bande\fR
.LP
\fIS:\ se\o"n~"alizaci\*'on fuera de banda\fR
.PP
The exchange of control signals between interconnected DCEs using signals
other than those for the transmission of data in the forward channel. The
transmission of DTE data is not disrupted.
.RT
.sp 2P
.LP
\fB7\fR \fBcoded inband signalling\fR
.sp 1P
.RT
.LP
\fIF:\ signalisation dans la bande avec codage\fR
.LP
\fIS:\ se\o"n~"alizaci\*'on codificada dentro de banda\fR
.PP
Inband signalling by which control signals are exchanged via data in the
forward channel.
.RT
.sp 2P
.LP
\fB8\fR \fBhalf\(hyduplex operation\fR
.sp 1P
.RT
.LP
\fIF:\ exploitation en semi\(hyduplex\fR
.LP
\fIS:\ explotaci\*'on (o funcionamiento) semid\*'uplex\fR
.PP
The exchange of data in either direction, one direction at a
time.
.RT
.sp 2P
.LP
\fB9\fR \fBinterface rate\fR
.sp 1P
.RT
.LP
\fIF:\ d\*'ebit \*`a l'interface\fR
.LP
\fIS:\ velocidad de interfaz\fR
.PP
The transfer rate of the bit stream found on the physical
interchange circuits.
.RT
.sp 2P
.LP
\fB10\fR \fBinformation rate\fR
.sp 1P
.RT
.LP
\fIF:\ d\*'ebit d'information\fR
.LP
\fIS:\ velocidad de informaci\*'on\fR
.PP
The transfer of information bits (the equivalent of the bit rate of circuit\
103 or\ 104 on a V.24 interface).
.RT
.sp 2P
.LP
\fB11\fR \fBcontrol signalling rate\fR
.sp 1P
.RT
.LP
\fIF:\ d\*'ebit de la signalisation de commande\fR
.LP
\fIS:\ velocidad de se\o"n~"alizaci\*'on de control\fR
.PP
The transfer rate of the encoded and multiplexed control
signalling (the equivalent of V.24 and V.25 interchange circuits, except the
data and timing circuits, insofar as required for an application, with the
possibility of adding other signalling).
.bp
.RT
.sp 2P
.LP
\fB12\fR \fBparallel automatic calling\fR
.sp 1P
.RT
.LP
\fIF:\ appel automatique en parall\*`ele\fR
.LP
\fIS:\ llamada autom\*'atica paralelo; llamada autom\*'atica en modo\fR
\fIparalelo\fR
.PP
A procedure by which a DTE, by use of the 200\ series interchange circuits,
may instruct a DCE to perform the call establishment function. The
transmission, from DTE to DCE, of each digit to be dialled is achieved in
parallel form on interchange circuits\ 206 to\ 209.
.RT
.sp 2P
.LP
\fB13\fR \fBserial automatic calling\fR
.sp 1P
.RT
.LP
\fIF:\ appel automatique en s\*'erie\fR
.LP
\fIS:\ llamada autom\*'atica serie; llamada autom\*'atica en modo serie\fR
.PP
A procedure by which a DTE, by use of the 100\ series interchange circuits,
may instruct a DCE to perform the call establishment function. The
transmission from DTE to DCE, of each digit to be dialled, is achieved in
serial form on interchange circuit\ 103.
.RT
.sp 2P
.LP
\fB14\fR \fBstart\(hystop transmission\fR
.sp 1P
.RT
.LP
\fIF:\ transmission arythmique\fR
.LP
\fIS:\ transmisi\*'on arr\*'itmica\fR
.PP
A form of anisochronous transmission in which each group of
contiguous data units is preceded by a start signal and is terminated by
a stop signal.
.RT
.LP
.rs
.sp 32P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.ce 1000
\v'3P'
SECTION\ 2
.ce 0
.sp 1P
.ce 1000
\fBINTERFACES\ AND\ VOICE\(hyBAND\ MODEMS\fR \v'1P'
.ce 0
.sp 1P
.sp 2P
.LP
\fBRecommendation\ V.10\fR
.RT
.sp 2P
.ce 1000
\fBELECTRICAL\ CHARACTERISTICS\ FOR\ \fR \fBUNBALANCED\fR
.EF '% Fascicle\ VIII.1\ \(em\ Rec.\ V.10''
.OF '''Fascicle\ VIII.1\ \(em\ Rec.\ V.10 %'
.ce 0
.ce 1000
\fBDOUBLE\(hyCURRENT\ INTERCHANGE\ CIRCUITS\ \fR \fBFOR\ GENERAL\ USE\fR
.ce 0
.ce 1000
\fBWITH\ \fR \fBINTEGRATED\ CIRCUIT\ EQUIPMENT\fR
.ce 0
.sp 1P
.ce 1000
\fBIN\ THE\ FIELD\ OF\ DATA\ COMMUNICATIONS\fR \|
.FS
This
Recommendation is also designated as X.26 in the Series\ X
Recommendations.
.FE
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1976; amended at Geneva, 1980 and at Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR \fBIntroduction\fR
.sp 1P
.RT
.PP
This Recommendation deals with the electrical characteristics of
the generator, receiver and interconnecting leads of an unbalanced interchange
circuit employing a differential receiver.
.PP
In the context of this Recommendation an unbalanced interchange
circuit is defined as consisting of an unbalanced generator connected to a
receiver by an interconnecting lead and a common return lead.
.PP
Annexes and Appendices are provided to give guidance on a number of
application aspects as follows:
.RT
.LP
\fIAnnex\ A\fR Compatibility with other interfaces
.LP
\fIAnnex\ B\fR Considerations for coaxial cable applications \(em
V.10 COAXIAL
.LP
\fIAppendix\ I\fR
Waveshaping
.LP
\fIAppendix\ II\fR Cable guidelines
.PP
\fINote\fR \ \(em\ Generator and load devices meeting the electrical
characteristics of this Recommendation need not operate over the entire data
signalling rate range specified. They may be designed to operate over narrower
ranges to satisfy specific requirements more economically, particularly
at
lower data signalling rates.
.PP
The interconnecting cable is normally not terminated, but the matter of
terminating coaxial interconnecting cable is dealt with in Annex\ B. Where
the interchange circuit incorporates the special provisions for coaxial
applications with cable termination this shall be referred to as \*Qcomplying
with Recommendation\ V.10 (COAXIAL)\*U.
.PP
Reference measurements are described which may be used to verify
certain of the recommended parameters but it is a matter for individual
manufacturers to decide what tests are necessary to ensure compliance with
the Recommendation.
.RT
.LP
.sp 1
.bp
.sp 2P
.LP
\fB2\fR \fBField of application\fR
.sp 1P
.RT
.PP
The electrical characteristics specified in this Recommendation
apply to interchange circuits operating with data signalling rates up to
100\ kbit/s
.FS
Signalling rates above the suggested 100\ kbit/s may also be
employed, but the maximum suggested operating distances should be shortened
accordingly (see Figure\ II\(hy1/V.10).
.FE
, and are intended to be used primarily in
Data Terminal Equipment (DTE)
and
Data Circuit\(hyterminating
Equipment (DCE)
implemented in integrated circuit technology.
.PP
This Recommendation is not intended to apply to equipment implemented in
discrete component technology, for which the electrical characteristics
covered by Recommendation\ V.28 are more appropriate.
.PP
Typical points of application are illustrated in Figure\ 1/V.10.
.RT
.LP
.rs
.sp 27P
.ad r
\fBFigure\ 1/V.10, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
Whilst the unbalanced interchange circuit is primarily intended
for use at the lower data signalling rates, its use should be avoided in the
following cases:
.LP
1)
where the interconnecting cable is too long for proper
unbalanced circuit operation;
.LP
2)
where extraneous noise sources make unbalanced circuit
operation impossible;
.LP
3)
where it is necessary to minimize interference with other
signals.
.PP
Whilst a restriction on maximum cable length is not specified,
guidelines are given with respect to conservative operating distance as a
function of data signalling rates (see Appendix\ II).
.LP
.sp 1
.bp
.sp 2P
.LP
\fB3\fR \fBSymbolic representation of an interchange circuit\fR \|
(Figure\ 2/V.10)
.sp 1P
.RT
.LP
.rs
.sp 47P
.ad r
\fBFigure\ 2/V.10, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
For data transmission applications, it is commonly accepted that the interface
cabling is provided by the DTE. This introduces the line of
demarcation between the DTE plus cable and the DCE. This line is also called
the interchange point and physically implemented in the form of a connector.
The applications also require interchange circuits in both directions. This
leads to an illustration as shown in Figure\ 3/V.10.
.bp
.LP
.rs
.sp 41P
.ad r
\fBFigure 3/V.10, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB4\fR \fBGenerator polarities\fR \fBand\fR
\fBreceiver significant\fR
\fBlevels\fR
.sp 1P
.RT
.sp 1P
.LP
4.1
\fIGenerator\fR
.sp 9p
.RT
.PP
The signal conditions for the generator are specified in terms of the voltage
between output points\ A and C shown in Figure\ 2/V.10.
.PP
When the signal condition\ 0 (space) for data circuits, or ON for
control and timing circuits, is transmitted the output point\ A is positive
with respect to point\ C. When the signal condition\ 1 (mark) for data
circuits, or
OFF for control and timing circuits, is transmitted the output point\ A is
negative with respect to point\ C.
.bp
.RT
.sp 1P
.LP
4.2
\fIReceiver\fR
.sp 9p
.RT
.PP
The receiver significant levels are shown in Table\ 1/V.10, where
\fIV\fR \s6A`
.PS 10
and \fIV\fR \s6B`
.PS 10
are respectively the
voltage at points\ A` and B` relative to point\ C`.
.RT
.ce
\fBH.T. [T1.10]\fR
.ce
TABLE\ 1/V.10
.ce
\fBReceiver significant levels\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(48p) .
T{
\fIV\fR
A
` \(em \fIV\fR
B
` \(= \(em0.3 V
T} T{
\fIV\fR
A
` \(em \fIV\fR
B
` \(>=" +0.3 V
T}
.T&
lw(84p) | cw(48p) | cw(48p) .
Data circuits 1 0
_
.T&
lw(84p) | cw(48p) | cw(48p) .
Control and timing circuits OFF ON
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 1/V.10 [T1.10], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 2
.sp 2P
.LP
\fB5\fR \fBGenerator\fR
.FS
For test purposes other than specified in
this Recommendation (e.g.\ signal quality measurement), a transmitter test
load of 450\ ohms may be used.
.FE
.sp 1P
.RT
.sp 1P
.LP
5.1
\fIOutput impedance\fR
.sp 9p
.RT
.PP
The total dynamic output impedance of the generator shall be equal to or
less than 50\ ohms.
.RT
.sp 1P
.LP
5.2
\fIStatic reference measurements\fR
.sp 9p
.RT
.PP
The generator characteristics are specified in accordance with
measurements illustrated in Figure\ 4/V.10 and described in \(sc\(sc\ 5.2.1
to 5.2.4\ below.
.RT
.sp 1P
.LP
5.2.1
\fIOpen circuit measurement\fR \|[Figure\ 4a)/V.10]
.sp 9p
.RT
.PP
The open circuit voltage measurement is made with a 3900\(hyohm
resistor connected between points\ A and\ C. In both binary states, the
magnitude of the signal voltage\ (\fIV\fR\d0\u) shall be equal to or greater
than
4.0\ volts but not greater than 6.0\ volts.
.RT
.sp 1P
.LP
5.2.2
\fITest termination measurement\fR \|[Figure\ 4b)/V.10]
.sp 9p
.RT
.PP
With a test load of 450\ ohms connected between output points\ A
and C, the magnitude of the output voltage (\fIV\fR\d\fIt\fR\u) in both binary
states shall be equal to or greater than\ 0.9 of the magnitude
of\ \fIV\fR\d0\u.
.RT
.sp 1P
.LP
5.2.3
\fIShort\(hycircuit measurement\fR \|[Figure 4c)/V.10]
.sp 9p
.RT
.PP
With the output points A and C short\(hycircuited the current
(\fII\fR\d\fIs\fR\u) flowing through point\ A in both binary states shall
not exceed 150\ milliamperes.
.RT
.sp 1P
.LP
5.2.4
\fIPower\(hyoff measurements\fR \|[Figure 4d)/V.10]
.sp 9p
.RT
.PP
Under power\(hyoff condition, with a voltage ranging between
+0.25\ volt and \(em0.25\ volt applied between the output point\ A and
point\ C, the magnitude of the output leakage current (\fII\fR\d\fIx\fR\u)
shall not exceed
100\ micro
amperes.
.RT
.LP
.sp 1
.bp
.LP
.rs
.sp 30P
.ad r
\fBFigure\ 4/V.10, (MC), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
5.3
\fIGenerator output rise\(hytime measurement\fR \|(Figure 5/V.10)
.sp 1P
.RT
.sp 1P
.LP
5.3.1
\fIWaveform\fR
.sp 9p
.RT
.PP
The measurement will be made with a resistor of 450\ ohms connected between
points\ A and C. A test signal, with a nominal signal element duration
\fIt\fR\d\fIb\fR\uand composed of alternate ones and zeros, shall be applied
to the
input. The change in amplitude of the output signal during transitions from
one binary state to the other shall be monotonic between\ 0.1 and\ 0.9
of\ \fIV\fR \s6\fIss\fR .PS 10
.
.RT
.sp 1P
.LP
5.3.2
\fIWaveshaping\fR
.sp 9p
.RT
.PP
Waveshaping of the generator output signal shall be employed to
control the level of interference (near\(hyend crosstalk) which may be coupled
to adjacent circuits in an interconnection. The rise time (\fIt\fR\d\fIr\fR\u)
of
the output signal shall be controlled to ensure the signal reaches
0.9\ \fIV\fR \s6\fIss\fR .PS 10
between 0.1 and 0.3 of the duration of the unit interval (\fIt\fR\d\fIb\fR\u)
at signalling rates greater than 1\ kbit/s, and between 100 and 300\ microseconds
at signalling rates of 1\ kbit/s or less. The method of waveshaping is
not specified but examples are given in Appendix\ I.
.bp
.RT
.LP
.rs
.sp 31P
.ad r
\fBFigure\ 5/V.10, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB6\fR \fBLoad\fR
.sp 1P
.RT
.sp 1P
.LP
6.1
\fICharacteristics\fR
.sp 9p
.RT
.PP
The load consists of a receiver (R) as shown in Figure\ 2/V.10. The electrical
characteristics of the receiver are specified in terms of the
measurements illustrated in Figures\ 6/V.10, 7/V.10 and\ 8/V.10 and described
in \(sc\(sc\ 6.2, 6.3 and\ 6.4 below. A circuit meeting these requirements
results in a
differential receiver having a high input impedance, a small input threshold
transition region between \(em0.3\ and +0.3\ volts differential, and allowance
for an internal bias voltage not to exceed 3\ volts in magnitude.
.PP
The receiver is electrically identical to that specified for the
balanced receiver in Recommendation\ V.11.
.RT
.sp 1P
.LP
6.2
\fIReceiver input voltage\ \(em\ current measurements\fR \|
(Figure\ 6/V.10)
.sp 9p
.RT
.PP
With the voltage \fIV\fR \s6\fIia\fR .PS 10
(or
\fR
\fIV\fR \s6\fIib\fR .PS 10
) ranging between
\(em10\ volts and +10\ volts, while \fIV\fR \s6\fIib\fR .PS 10
(or
\fIV\fR \s6\fIia\fR .PS 10
) is held at 0\ volt,
the resultant input current \fII\fR \s6\fIia\fR .PS 10
(or
\fII\fR \s6\fIib\fR .PS 10
) shall remain within
the shaded range shown in Figure\ 6/V.10. These measurements apply with the
power supply of the receiver in both the power\(hyon and power\(hyoff
conditions.
.bp
.RT
.LP
.rs
.sp 9P
.ad r
\fBFigure 6/V.10, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
6.3
\fIDC input \fR \fIsensitivity measurements\fR \|(Figure 7/V.10)
.sp 9p
.RT
.PP
Over the entire common\(hymode voltage
(\fIV\fR \s6\fIcm\fR .PS 10
) range of +7\ volts to \(em7\ volts, the receiver shall not require a
differential input voltage (\fIV\fR\d\fIi\fR\u) of more than
300\ millivolts to assume correctly the intended binary state. Reversing the
polarity of \fIV\fR\d\fIi\fR\ushall cause the receiver to assume the opposite
binary
state.
.RT
.LP
.rs
.sp 35P
.ad r
\fBFigure 7/V.10, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.PP
The maximum voltage (signal plus common\(hymode) present between
either receiver input and receiver ground shall not exceed 10\ volts nor
cause the receiver to malfunction. The receiver shall tolerate a maximum
differential voltage of 12\ volts applied across its input terminals without
being
damaged.
.PP
In the presence of the combinations of input voltages
\fIV\fR \s6\fIia\fR .PS 10
and \fIV\fR \s6\fIib\fR .PS 10
specified in
Figure\ 7/V.10, the receiver shall maintain the specified output binary state
and shall not be damaged.
.RT
.PP
\fINote\fR \ \(em\ Designers of equipment should be aware that slow signal
transitions with noise present may give rise to instability or
oscillatory conditions in the receiving equipment; therefore, appropriate
techniques should be implemented to prevent such behaviour. For example,
adequate hysteresis may be incorporated in the receiver to prevent such
conditions.
.RT
.sp 1P
.LP
6.4
\fIInput balance test\fR \| (Figure\ 8/V.10)
.sp 9p
.RT
.PP
The balance of the receiver input resistances and internal bias
voltages shall be such that the receiver shall remain in the intended binary
state under the conditions shown in Figure\ 8/V.10 and described as
follows:
.RT
.LP
a)
with \fIV\fR\d\fIi\fR\u\ =\ +720\ millivolts and
\fIV\fR \s6\fIcm\fR .PS 10
varied between \(em7 and +7\ volts;
.RT
.LP
b)
with \fIV\fR\d\fIi\fR\u\ =\ \(em720\ millivolts and
\fIV\fR \s6\fIcm\fR .PS 10
varied between \(em7 and +7\ volts;
.RT
.LP
c)
with \fIV\fR\d\fIi\fR\u\ =\ +300\ millivolts and
\fIV\fR \s6\fIcm\fR .PS 10
a 1.5\ volt peak\(hyto\(hypeak square wave
at the highest applicable data signalling rate (this condition
is provisional and subject to further study);
.RT
.LP
d)
with \fIV\fR\d\fIi\fR\u\ =\ \(em300\ millivolts and
\fIV\fR \s6\fIcm\fR .PS 10
a 1.5\ volt peak\(hyto\(hypeak square wave
at the highest applicable data signalling rate (this condition
is provisional and subject to further study).
.RT
.PP
\fINote\fR \ \(em\ The values of \fIV\fR\d\fIi\fR\u\| are provisional and
are the
subject of further study.
.LP
.rs
.sp 13P
.ad r
\fBFigure\ 8/V.10, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB7\fR \fBEnvironmental constraints\fR
.sp 1P
.RT
.PP
In order to operate an unbalanced interchange circuit at data
signalling rates ranging between 0 and 100\ kbit/s, the following conditions
apply:
.RT
.LP
1)
The total peak differential noise measured between the
points\ A` and\ B` at the load interchange point (with the
generator interchange point connected to a 50\(hyohm resistor
substituted for the generator) shall not exceed the expected
amplitude of the received signal minus 0.3\ volts
(provisional value).
.LP
2)
The worst\(hycase combination of generator\(hyreceiver ground
potential difference (\fIV\fR\d\fIg\fR\u, Figure\ 2/V.10) and
longitudinally induced peak random noise voltage measured
between the receiver points\ A` or\ B` and\ C` with the
generator ends of the cable\ A and\ C joined together
shall not exceed 4\ volts.
.sp 2P
.LP
\fB8\fR \fBCircuit protection\fR
.sp 1P
.RT
.PP
Unbalanced generator and load devices complying with this
Recommendation shall not be damaged under the following conditions:
.RT
.LP
1)
generator open circuit;
.LP
2)
short\(hycircuit between the conductors of the
interconnecting cable;
.LP
3)
short\(hycircuit between the conductors and Point\ C
or\ C`.
.bp
.PP
The above faults\ 2) and 3) might cause power dissipation in the
interchange circuit devices to approach the maximum power dissipation that
may be tolerated by a typical integrated circuit (IC) package. The user
is
therefore cautioned that where multiple generators and receivers are
implemented in a single IC package, only one such fault per package might be
tolerable at any one time without damage occurring.
.PP
The user is also cautioned that the generator and receiver devices
complying with this Recommendation might be damaged by spurious voltages
applied between their input or output points and points\ C and\ C`
(Figure\ 2/V.10). In those applications where the interconnecting cable
may be inadvertently connected to other circuits or where it may be exposed
to a
severe electromagnetic environment, protection should be
employed.
.RT
.sp 2P
.LP
\fB9\fR \fBCategory 1 and category 2 receivers\fR
.sp 1P
.RT
.PP
In order to provide flexibility in the choice of generator
(V.10\ or\ V.11), two categories of receiver are defined as
follows:
.RT
.LP
\fICategory\ 1\fR \ \(em\ Receivers shall have both input terminals\
A` and\ B`
connected to individual terminals at the load interchange point,
independent of all other receivers, as shown in Figure\ 9/V.10, and as
applied in Annex\ A, Figure\ A\(hy1/V.10.
.LP
\fICategory\ 2\fR \ \(em\ Receivers shall have one terminal connection for
each A` input terminal at the load interchange point, and all\ B` input
terminals shall be connected together within the DCE or DTE and shall
be brought to one common\ B` input terminal as shown in
Figure\ 10/V.10.
.PP
The specification of the category to be used in any application is part
of the appropriate DCE Recommendation, using this type of interface
electrical characteristics.
.LP
.rs
.sp 34P
.ad r
\fBFigure\ 9/V.10, (M), p.11\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 38P
.ad r
\fBFigure\ 10/V.10, (M), p.12\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB10\fR \fBSignal common return\fR
.sp 1P
.RT
.PP
The interconnection between the generator and the load interchange points
in Figure\ 2/V.10 shall consist of a signal conductor for each circuit
and one signal common return for each direction as shown in Figures\ 9/V.10
and\ 10/V.10. Signal common return may be implemented by more than one lead,
where required to accomplish interworking, as described in \(sc\ A.2
and as shown in Figure\ A\(hy1/V.10.
.PP
To minimize the effects of ground potential difference \fIV\fR\d\fIg\fR\uand
longitudinally\(hycoupled noise on the signal at the load interchange point,
the signal common return shall be connected to ground only at the C\ terminal
of the generator interchange point. For example, the B` terminal of all
the receivers in DTE which interconnect with unbalanced generators in DCE
shall connect to
signal common return circuit\ 102b, which is connected to ground only in\ DCE.
Signal common return circuit\ 102a is used to interconnect terminal\ B` of the
receivers in DCE with the grounded terminal\ C of the unbalanced generators
in\ DTE, as in Figures\ 9/V.10 and\ 10/V.10.
.bp
.RT
.sp 2P
.LP
\fB11\fR \fBDetection of generator power\(hyoff or circuit failure\fR
.sp 1P
.RT
.PP
Certain applications require detection of various fault conditions in the
interchange circuits, e.g.:
.RT
.LP
1)
generator power\(hyoff condition;
.LP
2)
receiver not interconnected with a generator;
.LP
3)
open\(hycircuited interconnecting cable;
.LP
4)
short\(hycircuited interconnecting cable;
.LP
5)
input signal to the load remaining within the transition
region (\(+-\|300\ millivolts) for an abnormal period of time.
.PP
When detection of one or more fault conditions is required by
specific applications, additional provisions are required in the load and
the following items must be determined:
.LP
a)
which interchange circuits require fault detection;
.LP
b)
what faults must be detected;
.LP
c)
what action must be taken when a fault is detected, e.g.
which binary state must the receiver assume?
.PP
The interpretation of a fault condition by a receiver (or load) is application
dependent. Each application may use a combination of the following classification:
.LP
\fIType\ 0\fR \ \(em\ No interpretation. A receiver or load does not
have fault
detection capability.
.LP
\fIType\ 1\fR \ \(em\ Data circuits assume a binary 1 state. Control
and timing
circuits assume an OFF condition.
.LP
\fIType\ 2\fR \ \(em\ Data circuits assume binary 0 state. Control and
timing circuits assume an ON condition.
.LP
\fIType\ 3\fR \ \(em\ Special interpretation. The receiver or load provides
a special indication for interpreting a fault condition. This special
indication requires further study.
.PP
The association of the circuit failure detection to particular
interchange circuits in accordance with the above types is a matter of the
functional and procedural characteristics specification of the
interface.
.PP
The interchange circuits monitoring circuit fault conditions in the
general telephone network interfaces are indicated in
Recommendation\ V.24.
.PP
The interchange circuits monitoring circuit fault conditions in data network
interfaces are indicated in Recommendation\ X.24\ [1].
.PP
The receiver fault detection type required is specified in the
relevant DCE\ Recommendations.
.RT
.sp 2P
.LP
\fB12\fR \fBMeasurements at the \fR \fBphysical interchange point\fR
.sp 1P
.RT
.PP
The following information provides guidance for measurements when maintenance
persons examine the interface for proper operation at the
interchange point.
.RT
.sp 1P
.LP
12.1
\fIListing of essential measurements\fR
.sp 9p
.RT
.LP
\(em
open\(hycircuit measurements;
.LP
\(em
test\(hytermination measurement;
.LP
\(em
short\(hycircuit measurement;
.LP
\(em
generator output rise time;
.LP
\(em
d.c. input sensitivity measurements.
.sp 1P
.LP
12.2
\fIListing of optional measurements\fR
.sp 9p
.RT
.LP
\(em
the total generator resistance between points\ A and\ C shall be equal
to or less than 50\ ohms;
.LP
\(em
power\(hyoff measurements;
.LP
\(em
receiver input voltage espace\(hyespace current
measurements;
.LP
\(em
input balance test;
.LP
\(em
check of the required circuit fault detection (\(sc\ 11).
.PP
The parameters defined in this Recommendation are not necessarily measurable
at the physical interchange point. This is for further
study.
.bp
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation\ V.10)
.sp 9p
.RT
.ce 0
.ce 1000
\fBCompatibility with other interfaces\fR
.sp 1P
.RT
.ce 0
.sp 2P
.LP
A.1
\fICompatibility of Recommendation\ V.10 and Recommendation\ V.11\fR
\fIinterchange circuits in the same interface\fR
.sp 1P
.RT
.PP
The electrical characteristics of Recommendation\ V.10 are designed to
allow the use of balanced (see Recommendation\ V.11) and unbalanced circuits
within the same interface. For example, the balanced circuits may be used
for data and timing whilst the unbalanced circuits may be used for associated
control circuit functions.
.RT
.sp 1P
.LP
A.2
\fIRecommendation\ V.10 interworking with Recommendation\ V.11\fR
.sp 9p
.RT
.PP
The differential receiver specifications of Recommendations\ V.10
and V.11 are electrically identical. It is therefore possible to interconnect
an equipment using Recommendation\ V.10 receivers and generators on one
side of the interface with an equipment using Recommendation\ V.11 generators
and
receivers on the other side of the interface. Such interconnection would
result in interchange circuits according to Recommendation\ V.11 in one
direction and interchange circuits according to Recommendation\ V.10 in the
other direction. Where such interworking is contemplated, the following
technical considerations must be taken into account.
.RT
.PP
A.2.1
Interconnecting cable lengths are limited by performance of the
circuits working to the Recommendation\ V.10 side of the interface.
.PP
A.2.2
The optional cable termination resistance (\fIZ\fR\d\fIt\fR\u), if
implemented, in the equipment using Recommendation\ V.11 must be
removed.
.PP
A.2.3
V.10\(hytype receivers shall be of category\ 1 (see
Figure\ A\(hy1/V.10).
.sp 1P
.LP
A.3
\fIRecommendation\ V.10 interworking with Recommendation\ V.28\fR
.sp 9p
.RT
.PP
The unbalanced electrical characteristics of Recommendation\ V.10
have also been designed to permit limited interworking, under certain
conditions, with generators and receivers to Recommendation\ V.28. Where such
interworking is contemplated, the following technical limitations must be
considered:
.RT
.PP
A.3.1
Separate DTE and DCE signal return paths will not be available
at the Recommendation\ V.28 side of the interface.
.PP
A.3.2
Data signalling\(hyrate limitations according to
Recommendation\ V.28 shall apply.
.PP
A.3.3
Interconnecting cable lengths are limited by the
Recommendation\ V.28 performance restrictions.
.PP
A.3.4
Probability of satisfactory operation will be enhanced by
providing the maximum generator voltage possible on the
Recommendation\ V.10 side of the interface within the limitations
stipulated in Recommendation\ V.10.
.PP
A.3.5
Whilst Recommendation\ V.28 type generators may use potentials
in excess of 12\ volts, many existing equipments are designed to operate with
power supplies of 12\ volts or less. Where this is the case, no further
protection of Recommendation\ V.10 receivers is required; however, in the
general case, protection against excessively high voltages from
Recommendation\ V.28 generators must be provided for the Recommendation\ V.10
receivers.
.PP
A.3.6
Power\(hyoff detectors in Recommendation\ V.28 receivers may not
necessarily work with Recommendation\ V.10 generators.
.LP
.rs
.sp 07P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 35P
.ad r
\fBFigure\ A\(hy1/V.10, (M), p.13\fR
.sp 1P
.RT
.ad b
.RT
.ce 1000
ANNEX\ B
.ce 0
.ce 1000
(to Recommendation\ V.10)
.sp 9p
.RT
.ce 0
.ce 1000
\fBConsiderations for coaxial cable\fR
.sp 1P
.RT
.ce 0
.ce 1000
\fBapplications \(em V.10\ COAXIAL\fR
.FS
All the
electrical characteristics specified in Recommendation\ V.10 other than
those set down in this Annex are applicable to the coaxial cable case with
a cable case with a cable termination.
.FE
.ce 0
.PP
It is recognized that where coaxial cables are used for
interconnecting purposes it may be desirable to include a terminating
resistance at the receiver end of the cable. This is considered to be a
special case for which special generator characteristics are required.
The terminating resistance shall in no case be less than 50\ ohms and the
reference measurements under \(sc\(sc\ 5.2.2 and\ 5.3 shall be made with
a 50\(hyohm test termination
.FS
For
test purposes other than specified in this Recommendation (e.g.\ signal
quality measurement), a transmitter test load of 50\ ohms may be used.
.FE
. Use
of this special application will require appropriate agreement with the
proper authority.
.bp
.sp 1P
.RT
.PP
The alternative set of electrical characteristics applied in the coaxial
cable case is the following:
.sp 1P
.LP
5.2.2\|\fIbis\fR \ \ \fITest termination measurement\fR \|[Figure\ 4b)/V.10]
.sp 9p
.RT
.PP
With a test load (\fIR\fR\d\fIt\fR\u) of 50\ ohms connected between
output points\ A and\ C, the magnitude of the output voltage\ (\fIV\fR\d\fIt\fR\u)
shall be equal to or greater than\ 0.5 of the magnitude
of\ \fIV\fR\d0\u.
.RT
.sp 1P
.LP
5.3.1\|\fIbis\fR \ \ \fIWaveform\fR \|(Figure\ 5/V.10)
.sp 9p
.RT
.PP
The measurement will be made with a resistor of 50\ ohms connected between
points\ A and C. A test signal, with a nominal signal element
duration\ \fIt\fR\d\fIb\fR\uand composed of alternate ones and zeros, shall
be applied to the input. The change in amplitude of the output signal during
transitions from one binary state to the other shall be monotonic between\
0.1 and\ 0.9
of\ \fIV\fR \s6\fIss\fR .PS 10
.
.RT
.sp 1P
.LP
5.3.2\|\fIbis\fR \ \ \fIWaveshaping\fR
.sp 9p
.RT
.PP
Waveshaping is not normally required for coaxial cable
applications.
.RT
.sp 1P
.LP
10\|\fIbis\fR \ \ \fISignal common return\fR
.sp 9p
.RT
.PP
In applications where coaxial cables are used, the screen of the
coaxial cable shall be connected to ground only at point\ C at the generator
end as shown in Figure\ B\(hy1/V.10.
.RT
.LP
.rs
.sp 32P
.ad r
\fBFigure B\(hy1/V.10, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce 1000
APPENDIX\ I
.ce 0
.ce 1000
(to Recommendation V.10)
.sp 9p
.RT
.ce 0
.ce 1000
\fBWaveshaping\fR
.sp 1P
.RT
.ce 0
.PP
The required waveshaping may be accomplished either by
providing a slew\(hyrate control in the generator or by inserting an RC
filter at the generator interchange point. A combination of these methods
may also be
employed. An example of the RC filter method is shown in Figure\ I\(hy1/V.10.
Typical values of capacitance\ \fIC\fR\d\fIw\fR\u, with the value of \fIR\fR\d\fIw\fR\uselected
so that \fIR\fR\d\fIw\fR\u\ +\ \fIR\fR\d\fId\fR\uis approximately 50\ ohms,
are given for typical cable with an interconductor shunt capacitance of
approximately 0.05\ microfarads per kilometre.
.sp 1P
.RT
.LP
.rs
.sp 24P
.ad r
\fBFigure I\(hy1/V.10, (M), p.
.sp 1P
.RT
.ad b
.RT
.ce 1000
APPENDIX\ II
.ce 0
.ce 1000
(to Recommendation\ V.10)
.sp 9p
.RT
.ce 0
.ce 1000
\fBCable Guidelines\fR
.sp 1P
.RT
.ce 0
.PP
No electrical characteristics of the interconnection cable are
specified in this Recommendation. However, guidance is given herein
concerning operational constraints imposed by cable length and near\(hyend
crosstalk.
.sp 1P
.RT
.PP
The maximum operating distance for the unbalanced interchange
circuit is primarily a function of the amount of interference (near\(hyend
crosstalk) coupled to adjacent circuits in the equipment interconnection.
Additionally the unbalanced circuit is susceptible to exposure to differential
noise resulting from any imbalance between the signal conductor and signal
common return at the load interchange point. Increasing the physical separation
and interconnection cable length between the generator and load interchange
points might increase the exposure to common\(hymode noise and the degree of
near\(hyend crosstalk. Accordingly, users are advised to restrict the cable
length to a minimum consistent with the generator\(hyload physical separation
requirements.
.bp
.PP
The curve of cable length versus data signalling rate given in
Figure\ II\(hy1/V.10 may be used as a conservative guide. This curve is
based upon calculations and empirical data using twisted\(hypair telephone
cable with a shunt capacitance of 0.052\ microfarads per kilometre, a 50\(hyohm
source impedance, a
6\(hyvolt source signal and maximum near\(hyend crosstalk of 1\(hyvolt
peak. The rise
time (\fIt\fR\d\fIr\fR\u) of the source signal at signalling rates below
1000\ bit/s is 100\ microseconds and above 1000\ bit/s is 0.1\ \fIt\fR\d\fIb\fR\u(see
Figure\ 5/V.10).
.PP
The user is cautioned that the curve given in Figure\ II\(hy1/V.10 does
not account for common\(hymode noise or near\(hyend crosstalk levels beyond the
limits specified, that may be introduced between the generator and load by
exceptionally long cables. On the other hand operation within the
signalling\(hyrate and distance bounds of Figure\ II\(hy1/V.10 will usually
ensure
that the distortion of the signal appearing at the receiver input will be
acceptable. Many applications, however, can tolerate greater levels of
signal distortion, and correspondingly greater cable lengths can be employed.
The
generation of near\(hyend crosstalk can be reduced by increasing the amount of
waveshaping employed.
.PP
Experience has shown that in most practical cases the operating
distance at the lower data signalling rates may be extended to several
kilometres.
.RT
.LP
.rs
.sp 30P
.ad r
\fBFigure\ II\(hy1/V.10, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fBReference\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fIList of definitions for interchange circuits\fR
\fIbetween data terminal equipment (DTE) and data circuit\(hyterminating\fR
\fIequipment (DCE) on public data networks\fR , Vol.\ VIII,
Rec.\ X.24.
.bp
.sp 2P
.LP
\fBRecommendation\ V.11\fR
.RT
.sp 2P
.ce 1000
\fBELECTRICAL\ CHARACTERISTICS\ FOR\ \fR \fBBALANCED\ DOUBLE\(hyCURRENT\fR
.EF '% Fascicle\ VIII.1\ \(em\ Rec.\ V.11''
.OF '''Fascicle\ VIII.1\ \(em\ Rec.\ V.11 %'
.ce 0
.ce 1000
\fBINTERCHANGE\ CIRCUITS\fR \fB\ FOR\ GENERAL\ USE\ WITH\ \fR \fBINTEGRATED\
CIRCUIT\fR
.ce 0
.sp 1P
.ce 1000
\fBEQUIPMENT
\fB\ IN\ THE\ FIELD\ OF\ DATA\ COMMUNICATIONS\fR
.FS
This
Recommendation is also designated as X.27 in the Series\ X
Recommendations.
.FE
.ce 0
.sp 1P
.ce 1000
\fI(Geneva, 1976; amended Geneva, 1980 and at Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fB1\fR \fBIntroduction\fR
.sp 1P
.RT
.PP
This Recommendation deals with the electrical characteristics of
the generator, receiver and interconnecting leads of a differential signalling
(balanced) interchange circuit with an optional d.c. offset voltage.
.PP
The balanced generator and load components are designed to cause
minimum mutual interference with adjacent balanced or unbalanced interchange
circuits (see Recommendation\ V.10) provided that waveshaping is employed on
the unbalanced circuits.
.PP
In the context of this Recommendation, a balanced interchange circuit is
defined as consisting of a balanced generator connected by a balanced
interconnecting pair to a balanced receiver. For a balanced generator the
algebraic sum of both the outlet potentials, with respect to earth, shall be
constant for all signals transmitted; the impedances of the outlets with
respect to earth shall be equal. The degree of balance and other essential
parameters of the interconnecting pair is a matter for further study.
.PP
An Annex and two Appendices are provided to give guidance on a number of
application aspects as follows:
.RT
.LP
\fIAnnex\ A\fR Compatibility with other interfaces.
.LP
\fIAppendix\ I\fR
Cable and termination.
.LP
\fIAppendix\ II\fR Multipoint operation.
.PP
\fINote\fR \ \(em\ Generator and load devices meeting the electrical
characteristics of this Recommendation need not operate over the entire data
signalling rate range specified. They may be designed to operate over narrower
ranges to satisfy requirements more economically, particularly at lower
data
signalling rates.
.PP
Reference measurements are described which may be used to verify
certain of the recommended parameters but it is a matter for individual
manufacturers to decide what tests are necessary to ensure compliance with
the Recommendation.
.RT
.sp 2P
.LP
\fB2\fR \fBField of application\fR
.sp 1P
.RT
.PP
The electrical characteristics specified in this Recommendation
apply to interchange circuits operating with data signalling rates up to
10\ Mbit/s, and are intended to be used primarily in Data Terminal Equipment
(DTE) and Data Circuit\(hyterminating Equipment (DCE) implemented in
integrated\(hycircuit technology.
.PP
This Recommendation is not intended to apply to equipment implemented in
discrete component technology, for which the electrical characteristics
covered by Recommendation\ V.28 are more appropriate.
.PP
Typical points of application are illustrated in Figure\ 1/V.11.
.PP
Whilst the balanced interchange circuit is primarily intended for use at
the higher data signalling rates, its use at the lower rates may be
necessary in the following cases:
.RT
.LP
1)
where the interconnecting cable is too long for proper
unbalanced circuit operation;
.LP
2)
where extraneous noise sources make unbalanced circuit
operation impossible;
.LP
3)
where it is necessary to minimize interference with other
signals.
.LP
.sp 1
.bp
.LP
.rs
.sp 18P
.ad r
\fBFigure\ 1/V.11, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB3\fR \fBSymbolic representation of interchange circuit\fR \|
(Figure\ 2/V.11)
.sp 1P
.RT
.LP
.rs
.sp 29P
.ad r
\fBFigure\ 2/V.11, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.PP
The equipment at both sides of the interface may implement
generators as well as receivers in any combination. Consequently, the symbolic
representation of the interchange circuit, Figure\ 2/V.11 above, defines
a
generator interchange point as well as a load interchange point.
.PP
For data transmission applications, it is commonly accepted that the interface
cabling will be provided by the DTE. This introduces the line of
demarcation between the DTE plus cable and the DCE. This line is also called
the interchange point and physically implemented in the form of a connector.
The applications also require interchange circuits in both directions. This
leads to an illustration as shown in Figure\ 3/V.11.
.RT
.LP
.rs
.sp 31P
.ad r
\fBFigure\ 3/V.11, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB4\fR \fBGenerator polarities\fR \fBand\fR
\fBreceiver significant
levels\fR
.sp 1P
.RT
.sp 1P
.LP
4.1
\fIGenerator\fR
.sp 9p
.RT
.PP
The signal conditions for the generator are specified in terms of the voltage
between output points\ A and B shown in Figure\ 2/V.11.
.PP
When the signal condition\ 0 (space) for data circuits or ON for
control and timing circuits is transmitted, the output point\ A is positive
with respect to point\ B. When the signal condition\ 1 (mark) for data
circuits or OFF for control and timing circuits is transmitted, the output
point\ A is
negative with respect to point\ B.
.RT
.sp 1P
.LP
4.2
\fIReceiver\fR
.sp 9p
.RT
.PP
The receiver differential significant levels are shown in
Table\ 1/V.11, where \fIV\fR \s6A`
.PS 10
and \fIV\fR \s6B`
.PS 10
are respectively the voltages at points\ A` and B` relative to
point\ C`.
.bp
.RT
.ce
\fBH.T. [T1.11]\fR
.ce
TABLE\ 1/V.11
.ce
\fBReceiver differential significant levels\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(48p) .
T{
\fIV\fR
A
` \(em \fIV\fR
B
` \(= \(em0.3 V
T} T{
\fIV\fR
A
` \(em \fIV\fR
B
` \(>=" +0.3 V
T}
_
.T&
lw(84p) | cw(48p) | cw(48p) .
Data circuits 1 0
_
.T&
lw(84p) | cw(48p) | cw(48p) .
Control and timing circuits OFF ON
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 1/V.11 {T1.11], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
\fB5\fR \fBGenerator\fR
.FS
For test purposes other than specified in
this Recommendation (e.g.\ signal quality measurement), a transmitter test
load of 100\ ohms may be used.
.FE
.sp 1P
.RT
.sp 2P
.LP
5.1
\fIResistance and d.c. offset voltage\fR
.sp 1P
.RT
.PP
5.1.1
The total generator resistance between points\ A and B shall be
in the range of 50 to 100\ ohms and adequately balanced with
respect to point\ C.
(It is left for further study as to the degree of balance required both
statically and dynamically.)
.sp 9p
.RT
.PP
\fINote 1\fR \ \(em\ It is assumed that the value of the dynamic source
impedance is in the same range.
.PP
\fINote 2\fR \ \(em\ There may be integrated circuits in the field which
do not comply with the requirement of 50\ ohms as a minimum. If this causes
problems in certain applications (e.g.\ reflections), additional series
resistors of
approximately 33\ ohms at each of the generator output leads would correct
these problems, if the use of a cable termination is not possible (e.g.\
for V.10
compatibility).
.RT
.PP
5.1.2
The magnitude of the generator d.c. offset voltage (see \(sc\ 5.2.2
below) shall not exceed 3\ V under all operating conditions.
.sp 9p
.RT
.sp 1P
.LP
5.2
\fIStatic reference measurements\fR
.sp 9p
.RT
.PP
The generator characteristics are specified in accordance with
measurements illustrated in Figure\ 4/V.11 and described in \(sc\(sc\ 5.2.1
to\ 5.2.4
below.
.RT
.sp 1P
.LP
5.2.1
\fIOpen\(hycircuit measurement\fR \|[Figure\ 4a)/V.11]
.sp 9p
.RT
.PP
The open\(hycircuit voltage measurement is made with a 3900\(hyohm
resistor connected between points\ A and B. In both binary states, the
magnitude of the differential voltage (\fIV\fR\d0\u\fR ) shall not be more than
6.0\ volts, nor shall the magnitude of \fIV\fR \s60\fIa\fR .PS 10
and
\fIV\fR \s60\fIb\fR .PS 10
be more than 6.0\ volts.
.RT
.sp 1P
.LP
5.2.2
\fITest\(hytermination measurement\fR \|[Figure\ 4b)/V.11]
.sp 9p
.RT
.PP
With a test load of two resistors, each 50\ ohms, connected in
series between the output points\ A and B, the differential voltage
(\fIV\fR\d\fIt\fR\u) shall not be less than 2.0\ volts or 50% of the magnitude
of
\fIV\fR\d0\u, whichever is greater. For the opposite binary state the polarity
of \fIV\fR\d\fIt\fR\ushall be reversed (\(em\fIV\fR\d\fIt\fR\u). The difference
in the magnitudes of \fIV\fR\d\fIt\fR\uand \(em\fIV\fR\d\fIt\fR\ushall
be less than 0.4\ volt. The magnitude of the
generator offset voltage \fIV\fR \s60\fIs\fR .PS 10
measured between the centre of the test load and point\ C shall not be
greater than 3.0\ volts. The magnitude of the difference in the values
of\ \fIV\fR \s60\fIs\fR .PS 10
for one binary
state and the opposite binary state shall be less than 0.4\ volt.
.RT
.PP
\fINote\fR \ \(em\ Under some conditions this measurement does not determine
the degree of balance of the internal generator impedances to point\ C. It is
left for further study whether additional measurements are necessary to
ensure adequate balance in generator output impedances.
.RT
.sp 1P
.LP
5.2.3
\fIShort\(hycircuit measurement\fR \|[Figure\ 4c)/V.11]
.sp 9p
.RT
.PP
With the output points\ A and B short\(hycircuited to point\ C, the
current flowing through each of the output points\ A or B in both binary
states shall not exceed 150\ milliamperes.
.bp
.RT
.sp 1P
.LP
5.2.4
\fIPower\(hyoff measurements\fR \|[Figure\ 4d)/V.11]
.sp 9p
.RT
.PP
Under power\(hyoff condition with voltages ranging between +0.25\ volt
and \(em0.25\ volt applied between each output point and point\ C, as indicated
in Figure\ 4d)/V.11, the magnitude of the output leakage currents
(\fII\fR \s6\fIxa\fR .PS 10
\ and\ \fII\fR \s6\fIxb\fR .PS 10
) shall not
exceed 100\ microamperes.
.RT
.LP
.rs
.sp 32P
.ad r
\fBFigure 4/V.11, (MC), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
5.3
\fIDynamic voltage balance and rise time measurements\fR
\|(Figure\ 5/V.11)
.sp 9p
.RT
.PP
With the measurement configuration shown in Figure\ 5/V.11, a test signal
with a nominal signal element duration \fIt\fR\d\fIb\fR\uand composed of
alternate ones and zeros, shall be applied to the input. The change in
amplitude of the output signal during transitions from one binary state
to the other shall be
monotonic between 0.1 and 0.9 \fIV\fR \s6\fIss\fR .PS 10
within 0.1 of \fIt\fR\d\fIb\fR\uor 20\ nanoseconds, whichever is greater.
Thereafter the signal voltage shall
not vary more than 10% of \fIV\fR \s6\fIss\fR .PS 10
from the steady state
value.
.RT
.PP
The resultant voltage due to imbalance (\fIV\fR\dE\u) shall not exceed
0.4\ V peak\(hyto\(hypeak.
.RT
.sp 2P
.LP
\fB6\fR \fBLoad\fR
.sp 1P
.RT
.sp 1P
.LP
6.1
\fICharacteristics\fR
.sp 9p
.RT
.PP
The load consists of a receiver (R) and an optional cable
termination resistance (\fIZ\fR\d\fIt\fR\u) as shown in Figure\ 2/V.11. The
electrical characteristics of the receiver are specified in terms of the
measurements illustrated in Figures\ 6/V.11, 7/V.11 and\ 8/V.11 and described
in \(sc\(sc\ 6.2, 6.3 and\ 6.4 below. A circuit meeting these requirements
results in a
differential receiver having a high input impedance, a small input threshold
transition region between \(em0.3 and +0.3\ volts differential, and allowance
for an internal bias voltage not to exceed 3\ volts in magnitude.
.bp
.PP
The receiver is electrically identical to that specified for the
unbalanced receiver in Recommendation\ V.10.
.RT
.sp 1P
.LP
6.2
\fIReceiver input voltage \(em current measurements\fR \|(Figure\ 6/V.11)
.sp 9p
.RT
.PP
With the voltage \fIV\fR \s6\fIia\fR .PS 10
(or
\fIV\fR \s6\fIib\fR .PS 10
) ranging
between \(em10\ volts and +10\ volts, while \fIV\fR \s6\fIib\fR .PS 10
(or
\fIV\fR \s6\fIia\fR .PS 10
) is held at
0\ volt, the resultant input current \fII\fR \s6\fIia\fR .PS 10
(or
\fII\fR \s6\fIib\fR .PS 10
) shall remain
within the shaded range shown in Figure\ 6/V.11. These measurements apply
with the power supply of the receiver in both the power\(hyon and power\(hyoff
conditions.
.RT
.LP
.rs
.sp 31P
.ad r
\fBFigure\ 5/V.11, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 11P
.ad r
\fBFigure\ 6/V.11, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
6.3
\fID.c. input \fR \fIsensitivity measurements\fR \|(Figure\ 7/V.11)
.sp 9p
.RT
.PP
Over the entire common mode voltage
(\fIV\fR \s6\fIcm\fR .PS 10
) range of +7\ volts to \(em7\ volts, the receiver shall not require a
differential input voltage (\fIV\fR\d\fIi\fR\u) of more than
300\ millivolts to assume correctly the intended binary state. Reversing the
polarity of \fIV\fR\d\fIi\fR\ushall cause the receiver to assume the opposite
binary
state.
.RT
.PP
The maximum voltage (signal plus common mode) present between either receiver
input and receiver ground shall not exceed 10\ volts nor cause the
receiver to malfunction. The receiver shall tolerate a maximum differential
voltage of 12\ volts applied across its input terminals without being damaged.
.PP
In the presence of the combination of input voltages
\fIV\fR \s6\fIia\fR .PS 10
and \fIV\fR \s6\fIib\fR .PS 10
specified in
Figure\ 7/V.11, the receiver shall maintain the specified output binary state
and shall not be damaged.
.RT
.PP
\fINote\fR \ \(em\ Designers of equipment should be aware that slow signal
transitions with noise present may give rise to instability or oscillatory
conditions in the receiving equipment; therefore, appropriate techniques
should be implemented to prevent such behaviour. For example, adequate
hysteresis may be incorporated in the receiver to prevent such conditions.
.RT
.LP
.rs
.sp 38P
.ad r
\fBFigure\ 7/V.11, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
6.4
\fIInput balance test\fR \|(Figure\ 8/V.11)
.sp 9p
.RT
.PP
The balance of the receiver input resistance and internal bias
voltages shall be such that the receiver shall remain in the intended binary
state under the conditions shown in Figure\ 8/V.11 and described as
follows:
.RT
.LP
a)
with \fIV\fR\d\fIi\fR\u\ =\ +720\ millivolts and
\fIV\fR \s6\fIcm\fR .PS 10
varied between \(em7 and +7\ volts;
.RT
.LP
b)
with \fIV\fR\d\fIi\fR\u\ =\ \(em720\ millivolts and
\fIV\fR \s6\fIcm\fR .PS 10
varied between \(em7 and +7\ volts;
.RT
.LP
c)
with \fIV\fR\d\fIi\fR\u\ =\ +300\ millivolts and
\fIV\fR \s6\fIcm\fR .PS 10
a 1.5\ volt peak\(hyto\(hypeak square wave at the highest applicable data
signalling rate (this condition is provisional and subject
to further study);
.RT
.LP
d)
with \fIV\fR\d\fIi\fR\u\ =\ \(em300\ millivolts and
\fIV\fR \s6\fIcm\fR .PS 10
a 1.5\ volt\fR peak\(hyto\(hypeak square wave
at the highest applicable data signalling rate (this condition
is provisional and subject to further study).
.RT
.LP
.rs
.sp 13P
.ad r
\fBFigure 8/V.11, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
6.5
\fITerminator\fR
.sp 9p
.RT
.PP
The use of a cable terminating impedance (\fIZ\fR\d\fIt\fR\u) is
optional depending upon the specific environment in which the interchange
circuit is employed (see Appendix\ I). In no case shall the total load
resistance be less than 100\ ohms.
.RT
.sp 2P
.LP
\fB7\fR \fBEnvironmental constraints\fR
.sp 1P
.RT
.PP
In order to operate a balanced interchange circuit at data
signalling rates ranging between 0 and 10\ Mbit/s, the following conditions
apply:
.RT
.LP
1)
For each interchange circuit a balanced interconnecting
pair is required.
.LP
2)
Each interchange circuit must be appropriately terminated
(see Appendix\ I).
.LP
3)
The total common\(hymode voltage at the receiver must be less than 7\
volts peak.
.PP
The common mode voltage at the receiver is the worst case
combination of:
.LP
a)
generator\(hyreceiver ground\(hypotential difference
(\fIV\fR\d\fIg\fR\u, Figure\ 2/V.11);
.LP
b)
longitudinally induced random noise voltage measured between the receiver
points\ A` or B` and C` with the generator ends of
the cable\ A, B and C joined together; and
.LP
c)
generator d.c. offset voltage, if any.
.PP
Unless the generator is of a type which generates no d.c. offset voltage,
the sum of\ a) and\ b) above, which is the element of the common
mode voltage due to the environment of the interchange circuit, must be less
than 4\ volts peak.
.bp
.sp 2P
.LP
\fB8\fR \fBCircuit protection\fR
.sp 1P
.RT
.PP
Balanced generator and load devices complying with this
Recommendation shall not be damaged under the following conditions:
.RT
.LP
1)
generator open circuit;
.LP
2)
short\(hycircuit between the conductors of the interconnecting cable;
.LP
3)
short\(hycircuit between either or both conductors and point\ C or C`.
.PP
The above faults 2) and 3) might cause power dissipation in the
interchange circuit devices to approach the maximum power dissipation that
may be tolerable by a typical integrated circuit (IC) package. The user
is
therefore cautioned that where multiple generators and receivers are
implemented in a single IC package, only one such fault per package might be
tolerable at any one time without damage occurring.
.PP
The user is also cautioned that the generator and receiver devices
complying with this Recommendation might be damaged by spurious voltages
applied between their input or output points and points\ C or\ C`
(Figure\ 2/V.11). In those applications where the interconnecting cable
may be inadvertently connected to other circuits, or where it may be exposed
to a
severe electromagnetic environment, protection should be employed.
.RT
.sp 2P
.LP
\fB9\fR \fBDetection of generator power\(hyoff or circuit failure\fR
.sp 1P
.RT
.PP
Certain applications require detection of various fault conditions in the
interchange circuits, e.g.:
.RT
.LP
1)
generator power\(hyoff condition;
.LP
2)
receiver not interconnected with a generator;
.LP
3)
open\(hycircuited interconnecting cable;
.LP
4)
short\(hycircuited interconnecting cable;
.LP
5)
input signal to the load remaining within the transition
region (\(+-\|300\ millivolts) for an abnormal period of time.
.PP
When detection of one or more fault conditions is required by
specific applications, additional provisions are required in the load and
the following items must be determined:
.LP
a)
which interchange circuits require fault detection;
.LP
b)
what faults must be detected;
.LP
c)
what action must be taken when a fault is detected, e.g.
which binary state must the receiver assume?
.PP
The interpretation of a fault condition by a receiver (or load) is application
dependent. Each application may use a combination of the following classification:
.LP
\fIType\ 0\fR \ \(em\ No interpretation. A receiver or load does not have
fault detection capability.
.LP
\fIType\ 1\fR \ \(em\ Data circuits assume a binary 1 state. Control and
timing circuits assume an OFF condition.
.LP
\fIType\ 2\fR \ \(em\ Data circuits assume binary 0 state. Control and
timing circuits assume an ON condition.
.LP
\fIType\ 3\fR \ \(em\ Special interpretation. The receiver or load provides
a special indication for interpreting a fault condition. This
special indication requires further study.
.PP
The association of the circuit failure detection to particular
interchange circuits in accordance with the above types is a matter of the
functional and procedural characteristics specification of the interface.
.PP
The interchange circuits monitoring circuit fault conditions in the
general telephone network interfaces are indicated in Recommendation\ V.24.
.PP
The interchange circuits monitoring circuit fault conditions in public
data network interfaces are indicated in Recommendation\ X.24\ [1].
.PP
The receiver fault detection type required is specified in the
relevant DCE Recommendations.
.RT
.sp 2P
.LP
\fB10\fR \fBMeasurements at the
\fBphysical interchange point\fR
.sp 1P
.RT
.PP
The following information provides guidance for measurements when maintenance
persons examine the interface for proper operation at the
interchange point.
.bp
.RT
.sp 1P
.LP
10.1
\fIListing of essential measurements\fR
.sp 9p
.RT
.LP
\(em
the magnitude of the generator d.c. offset voltage under all operating
conditions;
.LP
\(em
open\(hycircuit measurements;
.LP
\(em
test\(hytermination measurement;
.LP
\(em
short\(hycircuit measurement;
.LP
\(em
dynamic voltage balance and rise time;
.LP
\(em
d.c. input sensitivity measurements.
.sp 1P
.LP
10.2
\fIListing of optional measurements\fR
.sp 9p
.RT
.LP
\(em
The total generator resistance between points A and B shall be equal
to or less than 100\ ohms and adequately balanced with
respect to point\ C. (It is left for further study as to the
degree of balance required both statically and dynamically);
.LP
\(em
power\(hyoff measurements;
.LP
\(em
receiver input voltage\(hycurrent measurements;
.LP
\(em
input balance test;
.LP
\(em
check of the required circuit fault detection (\(sc\ 9).
.PP
The parameters defined in this Recommendation are not necessarily measurable
at the physical interchange point. This is for further
study.
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation V.11)
.sp 9p
.RT
.ce 0
.ce 1000
\fBCompatibility with other interfaces\fR
.sp 1P
.RT
.ce 0
.LP
A.1
\fICompatibility of Recommendation V.10 and Recommendation V.11\fR
\fIinterchange circuits in the same interface\fR
.sp 1P
.RT
.PP
The electrical characteristics of Recommendation V.11 are designed to allow
the use of unbalanced (see Recommendation\ V.10) and balanced circuits
within the same interface. For example, the balanced circuits may be used
for data and timing whilst the unbalanced circuits may be used for associated
control circuit functions.
.RT
.sp 1P
.LP
A.2
\fIRecommendation V.11 interworking with Recommendation V.10\fR
.sp 9p
.RT
.PP
The differential receiver specifications of Recommendations V.10
and V.11 are electrically identical. It is therefore possible to interconnect
an equipment using Recommendation\ V.10 receivers and generators on one
side of the interface with an equipment using Recommendation\ V.11 generators
and
receivers on the other side of the interface. Such interconnection would
result in the interchange circuits according to Recommendation\ V.11 in
one direction and interchange circuits according to Recommendation\ V.10
in the other
direction. Where such interworking is contemplated, the following technical
considerations must be taken into account.
.RT
.PP
A.2.1
Interconnecting cable lengths are limited by performance
of the circuits working to the Recommendation\ V.10 side of the
interface.
.PP
A.2.2
The optional cable termination resistance (\fIZ\fR\d\fIt\fR\u), if
implemented, in the equipment using Recommendation\ V.11 must be
removed.
.PP
A.2.3
V.10\(hytype receivers shall be of category 1.
.sp 1P
.LP
A.3
\fIRecommendation V.11 interworking with Recommendation V.35\fR
.sp 9p
.RT
.PP
Equipment having interchange circuits according to
Recommendation\ V.11 is expected to interoperate with practical implementations
of the electrical characteristics defined in Recommendation\ V.35, Appendix\
II. Interoperation between a V.35 transmitter and a V.11\ receiver will
result in
shorter cable length than those indicated in Figure\ I\(hy1/V.11. This
is due to
the fact that the output voltage from the V.35 transmitter loaded by a
100\ ohms resistor has a minimum value of 0.44\ volts peak/peak, which
represents about
1/5 of the voltage of the V.11\ transmitter (2\ volts), as per
Figure\ 7/V.11.
.bp
.RT
.ce 1000
APPENDIX\ I
.ce 0
.ce 1000
(to Recommendation V.11)
.sp 9p
.RT
.ce 0
.ce 1000
\fBCable and termination\fR
.sp 1P
.RT
.ce 0
.PP
No electrical characteristics of the interconnecting cable are specified
in this Recommendation. Guidance is given herein concerning
operational constraints imposed by the length, balance and terminating
resistance of the cable.
.sp 1P
.RT
.sp 1P
.LP
I.1
\fICable\fR
.sp 9p
.RT
.PP
Over the length of the cable, the two conductors should have
essentially the same values of:
.RT
.LP
1)
capacitance to ground;
.LP
2)
longitudinal resistance and inductance;
.LP
3)
coupling to adjacent cables and circuits.
.sp 1P
.LP
I.2
\fICable length\fR
.sp 9p
.RT
.PP
The maximum permissible length of cable separating the generator
and the load in a point\(hyto\(hypoint application is a function of the data
signalling rate. It is further influenced by the tolerable signal distortion
and the environmental constraints such as ground potential difference and
longitudinal noise. Increasing the distance between generator and load might
increase the exposure to ground potential difference.
.PP
As an illustration of the above conditions, the curves of cable
length versus data signalling rate in Figure\ I\(hy1/V.11 may be used for
guidance.
.RT
.LP
.rs
.sp 28P
.ad r
\fBFigure\ I\(hy1/V.11, (M), p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.PP
These curves are based upon empirical data using twisted pair
telephone cable (0.51\(hymm wire diameter) both unterminated and terminated
in a 100\(hyohm resistive load. The cable length restrictions shown by
the curves are based upon the following assumed signal quality requirements
at the
load:
.LP
1)
signal rise and fall time equal to, or less than, one\(hyhalf the duration
of the signal element;
.LP
2)
a maximum voltage loss between generator and load of
6\ dB.
.PP
At the higher data signalling rates (see Figure I\(hy1/V.11) the
sloping portion of the curves shows the cable length limitation established
by the assumed signal rise and fall time requirements. The cable length has
been arbitrarily limited to 1000\ metres by the assumed maximum allowable
loss of\ 6\ dB.
.PP
These curves assume that the environmental limits specified in this
Recommendation have been achieved. At the higher data signalling rates these
conditions are more difficult to attain due to cable imperfections and
common\(hymode noise. Operation within the data signalling rate and distance
bounds of Figure\ I\(hy1/V.11 will usually ensure that distortion of the signal
appearing at the receiver input will be acceptable. Many applications,
however, can tolerate much greater levels of signal distortion and in these
cases
correspondingly greater cable lengths may be employed.
.PP
Experience has shown that in many practical cases the operating
distance at lower signalling rates may extend to several kilometres.
.PP
For synchronous transmission where the data and signal element timing are
transmitted in opposite directions, the phase relationship between the
two may need to be adjusted to ensure conformity with the relevant requirements
of signal quality at the interchange point.
.RT
.sp 1P
.LP
I.3
\fICable termination\fR
.sp 9p
.RT
.PP
The use of a cable termination resistance (\fIZ\fR\d\fIt\fR\u) is
optional and dependent on the specific application. At the higher data
signalling rates (above 200\ kbit/s) or at any data signalling rate where the
cable propagation delay is of the order of half the signal element duration
a termination should be used to preserve the signal rise time and minimize
reflections. The terminating impedance should match as closely as possible
the cable characteristic impedance in the signal spectrum.
.PP
Generally, a resistance in the range of 100 to 150 ohms will be
satisfactory, the higher values leading to lower power dissipation.
.PP
At the lower data signalling rates, where distortion and rise\(hytime are
not critical, it may be desirable to omit the termination in order to minimize
power dissipation in the generator.
\v'3P'
.RT
.ce 1000
APPENDIX\ II
.ce 0
.ce 1000
(to Recommendation V.11)
.sp 9p
.RT
.ce 0
.ce 1000
\fBMultipoint operation\fR
.sp 1P
.RT
.ce 0
.PP
For further study. A specification for multipoint operation
including the version ISO\ 8482 is under study.
.sp 1P
.RT
.sp 2P
.LP
\fBReference\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fIList of definitions for interchange circuits\fR
\fIbetween data terminal equipment (DTE) and data circuit\(hyterminating\fR
\fIequipment (DCE) on public data networks\fR , Vol.\ VIII, Rec.\ X.24.
.bp
.sp 2P
.LP
\fBRecommendation\ V.13\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBSIMULATED\ CARRIER\ CONTROL\fR
.EF '% Fascicle\ VIII.1\ \(em\ Rec.\ V.13''
.OF '''Fascicle\ VIII.1\ \(em\ Rec.\ V.13 %'
.ce 0
.sp 1P
.ce 1000
\fI(Melbourne, 1988)\fR \v'1P'
\v'6p'
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
The\ CCITT,
.sp 1P
.RT
.sp 1P
.LP
\fIconsidering\fR
.sp 9p
.RT
.PP
(a)
that there is a wide variety of duplex data systems
available;
.PP
(b)
that some data terminal equipment (DTE) operate 2\(hyway alternate over
these systems.
.sp 1P
.LP
\fIrecommends\fR
.sp 9p
.RT
.PP
that the following procedure be employed for simulated circuit\ 105 to
circuit\ 109 operation, when specifically called for in a CCITT
Recommendation.
.RT
.sp 2P
.LP
\fB1\fR \fBScope\fR
.sp 1P
.RT
.PP
This Recommendation applies wherever a requirement for control of a remote
circuit\ 109 by a local circuit\ 105 exists, and where switching OFF and
ON of a modem carrier is impossible or impractical. Examples of such
environments are:
.RT
.LP
\(em
sub\(hychannels of modems containing multiplex facilities;
.LP
\(em
modems with long equalizer/echo canceller training
sequences;
.LP
\(em
high efficiency multiplexers containing no control channels;
.LP
\(em
PCM channels used for 64\ bit/s data transmission.
.sp 2P
.LP
\fB2\fR \fBLocation of the simulation function\fR
.sp 1P
.RT
.PP
Within this Recommendation the function is described as though it were
located between the DTE and the remaining part of the data
circuit\(hyterminating equipment (DCE). Location with respect to the loop
device as defined in Recommendation\ V.54 is for further study.
.RT
.sp 2P
.LP
\fB3\fR \fBOperation\fR
.sp 1P
.RT
.PP
When circuit 105 is OFF the DCE will transmit a pattern of bits
(idle pattern) produced by scrambling a binary\ 1 with the polynominal
1\ +\ x\uD\dlF261\u3\d\ + x\uD\dlF261\u7\d, in lieu of data bits for that
port. No particular starting state is specified for the scrambler. When
circuit\ 105 turns ON, the DCE will immediately transmit a pattern of 8\
bits (ON pattern) produced by
scambling a binary\ 0 with the polynomial 1\ +\ x\uD\dlF261\u3\d\ + x\uD\dlF261\u7\d,
after which data bits are sent (Note\ 1). Circuit\ 106 may be turned ON
within 8\ bit
intervals after circuit\ 105 turns ON, and the first bit appearing on
circuit\ 103 after circuit\ 106 turns ON should be sent as the first data bit
(Note\ 2). When circuit\ 106 is turned ON before transmission of the ON
pattern has been completed, data bits appearing on circuit\ 103 are stored
in a data
buffer for subsequent transmission.
.PP
At the remote DCE circuit\ 109 is turned OFF whenever a sufficient
number of successive bits in the above idle pattern is detected (Note\ 3).
Circuit\ 109 is turned ON after detecting a pattern of 8\ bits produced by
scrambling a binary\ 0 with the polynominal 1\ +\ x\uD\dlF261\u3\d\ +\
x\uD\dlF261\u7\d (Note\ 4). Circuit \ 104 (received data) is held at binary\
1 when circuit\ 109 is OFF (see also Notes\ 5, 6, 7).
.bp
.PP
\fINote\ 1\fR \ \(em\ The starting state of the scrambler used for scrambling
a binary\ 0 with the polynomial 1\ +\ x\uD\dlF261\u3\d\ +\ x\uD\dlF261\u7\d
should be the same as
the ending scrambler state after scrambling binary\ 1.
.PP
\fINote\ 2\fR \ \(em\ Additional circuit\ 106 turn ON delays may be provided as
manufacturer's options.
.PP
\fINote\ 3\fR \ \(em\ The number of successive bits of the idle pattern
required to be detected to turn circuit\ 109 OFF is recommended to be 48\(hy64.
Before
circuit\ 109 turns\ OFF, the idle pattern may appear on circuit\ 104.
.PP
\fINote\ 4\fR \ \(em\ It is recommended that circuit\ 109 be turned ON
only if the ON pattern is preceded by a sufficient number of consecutive
scrambled ones.
The protection against failure to recognize the ON pattern when transmission
errors occur is subject to further study. The length of the ON pattern
required to be detected to turn circuit\ 109 ON is provisionally fixed
to\ 8.
.PP
\fINote\ 5\fR \ \(em\ Following an ON to OFF transition of circuit\ 105,
circuit\ 105 should be ignored for at least 128\ bit intervals so that
at least 128\ bits produced by scrambling a binary\ 1 are sent to the remote
modem.
.PP
\fINote\ 6\fR \ \(em\ When circuit 105 is OFF, precaution should be taken that
the output of the scrambler is not continuous\ 1, but rather is a 127\ bit
pseudo\(hyrandom sequence.
.PP
\fINote\ 7\fR \ \(em\ Circuit 109 may be erroneously turned ON at the time of
receiving the idle pattern, or circuit\ 109 may remain OFF at the time of
receiving the ON pattern, when transmission errors occur. It may also turn
OFF due to simulation by user data.
\v'2P'
.RT
.sp 2P
.LP
\fBRecommendation\ V.14\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBTRANSMISSION\ OF\ START\(hySTOP\ CHARACTERS\ OVER\|
SYNCHRONOUS\ BEARER\ CHANNELS\fR
.EF '% Fascicle\ VIII.1\ \(em\ Rec.\ V.14''
.OF '''Fascicle\ VIII.1\ \(em\ Rec.\ V.14 %'
.ce 0
.sp 1P
.ce 1000
\fI(Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.sp 2P
.LP
\fB1\fR \fBScope\fR
.sp 1P
.RT
.PP
1.1
This Recommendation describes a method of conveying start\(hystop
characters over synchronous bearer channels using an async\(hyto\(hysync
converter in the data signalling rate range of up to 19\|200\ bit/s. Start\(hystop
characters at signalling rates below or equal to 300\ bit/s can be conveyed
over synchronous bearer channels by oversampling at a signalling rate of
at least
1200\ bit/s.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The conversion method provided here replaces the
conversion method applied earlier to Recommendations\ V.22, V.22\|\fIbis\fR ,
V.26\|\fIter\fR and V.32.
.PP
1.2
This converter may be an intermediate device inserted into the
data lines of both circuit\ 103 in the transmitter and circuit\ 104 in the
receiver inside a synchronous DCE (see Figure\ A\(hy1/V.14 in Annex\ A), or a
stand\(hyalone unit in certain applications.
.sp 9p
.RT
.sp 2P
.LP
\fB2\fR \fBData signalling rates\fR
.sp 1P
.RT
.PP
The conversion method shall be limited to signalling rates of up to 19\|200\
bit/s preferring the standard signalling rates of Recommendation\ V.5.
.PP
The nominal signalling rates for both the start\(hystop characters and
the synchronous DCE shall be the same. The tolerance of the signalling
rate of the synchronous transmission shall be \(+-0.01%.
.bp
.RT
.sp 2P
.LP
\fB3\fR \fBSignalling rate ranges of the start\(hystop characters at the\fR
\fBconverter input\fR
.sp 1P
.RT
.PP
The conversion method is capable of tolerating the signalling rates of
the DTE in two ranges:
.RT
.LP
a)
basic range: +1% to \(em2.5%
.LP
b)
extended range: +2.3% to \(em2.5%
.PP
The use of the basic signalling rate range is preferred since it results
in lower distortion. The choice of range shall be made at the time of installation,
and shall be the same for both transmitter and receiver. It is
not intended to be under customer control.
.sp 2P
.LP
\fB4\fR \fBStart\(hystop character format\fR
.sp 1P
.RT
.PP
It shall be possible to condition the converter to accept the
following formats; viz:
.RT
.LP
a)
a one\(hyunit start element, followed by seven data units, and a stop
element of the unit in length (9\(hybit characters);
.LP
b)
a one\(hyunit start element, followed by eight data units, and a stop
element of one unit in length (10\(hybit characters);
.LP
c)
a one\(hyunit start element, followed by nine data units, and a stop
element of one unit in length (11\(hybit characters);
.PP
The converter may also accept characters consisting of:
.LP
d)
a one\(hyunit start element, followed by six data units, and a stop element
of one unit in length (8\(hybit characters).
.PP
Note that character formats c) and d) do not conform to
International Alphabet No.\ 5.
.PP
The character format selected shall be the same for both transmitter and
receiver. The characters shall be in accordance with Recommendation\ V.4
regardless of whether they conform to International Alphabet No.\ 5. It
shall be possible to transmit characters continuously or with any additional
continuous stop element of arbitrary length between characters.
.PP
\fINote\fR \ \(em\ In each of the four formats, data units can be replaced by
additional stop units. For example, format\ c) will allow 11\(hybit characters
consisting of a one\(hyunit start element, followed by eight data units
and a stop element of two units to be handled.
.RT
.sp 2P
.LP
\fB5\fR \fBMargin of the converter input\fR
.sp 1P
.RT
.PP
The effective net margin of the converter for transmitting of
start\(hystop characters applied to the input of the converter shall be at
least\ 40%. This figure is a subject for further study.
.RT
.sp 2P
.LP
\fB6\fR \fBSelection of synchronous or asynchronous modes of operation\fR
.sp 1P
.RT
.PP
Selection for synchronous or asynchronous modes of operation shall be provided
by switch (or similar means) enabling the user to perform normal
transmission and testing in each mode of operation, respectively.
.PP
In synchronous mode of operation the converter is totally bypassed in both
directions.
.RT
.sp 2P
.LP
\fB7\fR \fBAsync\(hyto\(hysync conversion method\fR
.sp 1P
.RT
.PP
The general method to handle the speed differences between the
intracharacter signalling rate of the start\(hystop characters and the data
signalling rate of the synchronous bearer channel will be the
insertion/deletion of stop elements at the transmitter and reinsertion of
deleted stop elements at the receiver. Means are provided to transfer
continuous start polarity (break signals) as well.
.RT
.sp 1P
.LP
7.1
\fITransmitter\fR
.sp 9p
.RT
.PP
In the transmit direction the start\(hystop characters shall be
adapted to the signalling rate of the synchronous bearer channel
by:
.RT
.LP
\(em
deleting stop elements in case of overspeed of the start\(hystop characters;
.LP
\(em
insertion of additional stop elements in case of underspeed of the start\(hystop
characters.
.bp
.sp 1P
.LP
7.1.1
\fIBasic signalling rate range\fR
.sp 9p
.RT
.PP
No more than one stop element shall be deleted for any eight
consecutive characters.
.RT
.sp 1P
.LP
7.1.2
\fIExtended signalling rate range\fR
.sp 9p
.RT
.PP
No more than one stop element shall be deleted for any four
consecutive characters.
.RT
.sp 1P
.LP
7.2
\fIReceiver\fR
.sp 9p
.RT
.PP
The intracharacter signalling rate provided by the converter shall be in
the range of the nominal data rate to the limit of the specified
overspeed tolerance, i.e.\ +1% in the basic and +2.3% in the extended data
signalling range. The length of the stop element shall not be reduced by
more than 12.5% for the basic signalling rate range (or 25% for the optional
extended signalling rate range) to allow for overspeed in the transmitting
terminal. The nominal length of the start and data elements for all characters
shall be the same.
.PP
\fINote\fR \ \(em\ Equipments exists in the field which delete stop elements
more frequently than specified in \(sc\(sc\ 7.1.1 and 7.1.2. However, in these
equipments there will always be at least one additional inserted stop element
between deleted stop elements.
.RT
.sp 2P
.LP
7.3
\fIBreak signal\fR
.sp 1P
.RT
.sp 1P
.LP
7.3.1
\fITransmitter\fR
.sp 9p
.RT
.PP
If the converter detects M to 2M + 3 bits all of \*Qstart\*U polarity,
where M is the number of bits per character in the selected format, the
converter shall transmit 2M\ +\ 3 bits of \*Qstop\*U polarity. If the converter
detects more than 2M\ +\ 3 bits all of \*Qstart\*U polarity the converter shall
transmit all these bits as \*Qstart\*U polarity.
.PP
\fINote\fR \ \(em\ The converter must receive at least 2M bits of \*Qstop\*U
polarity after the \*Qstart\*U polarity break signal in order to ensure that it
regains the character synchronism.
.RT
.sp 1P
.LP
7.3.2
\fIReceiver\fR
.sp 9p
.RT
.PP
The 2M + 3 or more bits of \*Qstart\*U polarity received from the
transmitting modem shall be transferred to the output of the converter,
and the character synchronism shall be regained from the following \*Qstop\*U
to \*Qstart\*U
transition.
.PP
\fINote\fR \ \(em\ In some earlier implementations an uninitiated NUL character
may precede the break signal at the output of the converter when no measures
have been taken to prevent this.
.RT
.sp 1P
.LP
7.4
\fITandem operation\fR
.sp 9p
.RT
.PP
Tandem operation between two ends comprising async\(hyto\(hysync
conversions can be established only by using cascaded synchronous bearer
channels.
.RT
.sp 1P
.LP
7.5
\fITesting facilities\fR
.sp 9p
.RT
.PP
All the tests recommended in the relevant Recommendations can be
performed in asynchronous operation as well, where this converter is used,
with the exception of self test end\(hyto\(hyend.
.RT
.LP
.rs
.sp 06P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation V.14)
.sp 9p
.RT
.ce 0
.ce 1000
\fBInclusion of an async\(hyto\(hysync converter into a synchronous DCE\fR
.sp 1P
.RT
.ce 0
.LP
.rs
.sp 34P
.ad r
\fBFigure A\(em1/V.14, (N), p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
\fINote\fR \ \(em\ Other interchange circuits which are provided are not
involved in the operation of the async\(hyto\(hysync converter but must
comply with the requirements of the relevant DCE Recommendations including
the conditions of the timing circuits (i.e.\ 113, 114 and\ 115) during
both the asynchronous and synchronous modes of operation.
.LP
.rs
.sp 08P
.ad r
BLANC
.ad b
.RT
.LP
.bp