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InfoMagic Standards 1994 January
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ccitt
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1988
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.rs
.\" Troff code generated by TPS Convert from ITU Original Files
.\" Not Copyright ( c) 1991
.\"
.\" Assumes tbl, eqn, MS macros, and lots of luck.
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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'3P'
SECTION\ 1
.ce 0
.sp 1P
.ce 1000
\fBGENERAL\ PRINCIPLES\ OF\ MAINTENANCE\fR
.ce 0
.sp 1P
.ce 1000
\fBAND\ MAINTENANCE\ ORGANIZATION\fR
.ce 0
.sp 1P
.sp 2P
.LP
\fBRecommendation\ M.70\fR
.RT
.sp 2P
.ce 1000
\fBGUIDING\ PRINCIPLES\ ON\ THE\ \fR \fBGENERAL\ MAINTENANCE\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.70''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.70 %'
.ce 0
.sp 1P
.ce 1000
\fBORGANIZATION\ FOR\ TELEPHONE\(hyTYPE\ INTERNATIONAL\ CIRCUITS\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBGeneral\fR
.sp 1P
.RT
.PP
In order to furnish guiding principles to Administrations, the
CCITT recommends the following principles for the general maintenance
organization for international circuits.
.RT
.PP
1.1
Definitions relating to the various maintenance elements, each representing
a set of functions, are given in Recommendations\ M.710
to\ M.725 for automatic circuits, and in Recommendations\ M.1012\ [1],
M.1013\ [2], M.1014\ [3] for leased and special circuits.
.sp 9p
.RT
.PP
1.2
The size and complexity of the maintenance organization will
depend on the particular case and the particular country concerned. In some
instances it may be possible to carry out all sets of functions from a
single location; in others only some of the functions might be combined
and carried
out from one location. The precise arrangement will depend on the
Administration concerned, and the CCITT limits itself to defining the functions
of the separate elements, leaving the manner in which the elements are
grouped to be determined by the Administration.
.LP
.PP
1.3
If a country so desires and/or if it judges that the complexity of its
international telecommunications so requires, the international maintenance
organization can be responsible for all types of circuit for which
Study\ Group\ IV makes recommendations.
.sp 2P
.LP
\fB2\fR \fBTypes of circuits\fR \fBto be catered for\fR
.sp 1P
.RT
.PP
The types of circuits to be catered for are as follows:
.PP
public circuits:
.RT
.LP
\(em
telephone circuits,
.LP
\(em
voice\(hyfrequency telegraph circuits,
.LP
\(em
phototelegraph circuits,
.LP
\(em
sound\(hyprogramme circuits, etc.;
.LP
leased circuits:
.LP
\(em
telephone circuits: point\(hyto\(hypoint and multiterminal,
.LP
\(em
voice\(hyfrequency telegraph circuits,
.LP
\(em
data circuits: point\(hyto\(hypoint and multiterminal,
.LP
\(em
multi\(hyfacility circuits, that is, phototelegraph plus
voice\(hyfrequency telegraph; speech plus voice\(hyfrequency telegraph;
simultaneous or alternative transmission,
.LP
\(em
phototelegraph circuits,
.LP
\(em
sound\(hyprogramme circuits, etc.
.bp
.sp 2P
.LP
\fB3\fR \fBMaintenance organization\fR
.sp 1P
.RT
.PP
The maintenance of international public telephone circuits relies upon
the ability of each Administration to fulfil the various functions and
responsibilities noted in the Series\ M\ Recommendations. Where such circuits
are manual, as opposed to automatic, it is assumed that the Administration
will
select and provide the relevant elements such as the \fIfault report point\fR
\fI(circuit)\fR and the \fItesting point (transmission)\fR together with
\fIcircuit\fR
\fIcontrol\fR and \fIsub\(hycontrol station\fR assignments as appropriate.
.PP
For automatic circuits all the elements noted in Recommendation\ M.710 apply.
.PP
Leased and special international circuits require the services of a
Transmission Maintenance Point (International Line) (TMP\(hyIL) which is
described in Recommendation\ M.1014\ [3]. The circuit control and sub\(hycontrol
functions and responsibilities on leased and special international circuits
are noted in
Recommendations\ M.1012\ [1] and\ M.1013\ [2] and include a close cooperation
with the TMP\(hyIL.
.PP
For operations at other levels (group, supergroup, etc.), specific
responsibilities are allotted to particular repeater stations. At each
level, maintenance is based on the appointment of a \fIcontrol station\fR
and one or more \fIsub\(hycontrol stations\fR Additional information concerning
control and
sub\(hycontrol stations follows in Recommendations\ M.80 and\ M.90 and is
supplemented by that contained in Recommendations\ M.1012\ [1] and M.1013\ [2],
M.723, M.724, N.5\ [4] and N.55\ [5].
.PP
The attention of Administrations is drawn to the need for exchanging contact
forms (similar to those for maintenance units for automatic circuits as
described in Recommendation\ M.93) which give telephone numbers, staffing
hours, etc. for units involved in the maintenance of leased circuits and the
higher order transmission systems.
.RT
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fICircuit control station for leased and special\fR
\fIcircuits\fR , Vol.\ IV, Rec.\ M.1012.
.LP
[2]
CCITT Recommendation \fISub\(hycontrol station for leased and special\fR
\fIcircuits,\fR Vol.\ IV, Rec.\ M.1013.
.LP
[3]
CCITT Recommendation \fITransmission maintenance point (international\fR
\fIline) (TMP\(hyIL)\fR , Vol.\ IV, Rec.\ M.1014.
.LP
[4]
CCITT Recommendation \fISound programme control, sub\(hycontrol and send\fR
\fIreference stations\fR , Vol.\ IV, Rec.\ N.5.
.LP
[5]
CCITT Recommendation \fIOrganization, responsibilities and functions
of\fR \fIcontrol and sub\(hycontrol stations for international television
connections,\fR \fIlinks, circuits and circuit sections\fR , Vol.\ IV,
Rec.\ N.55.
\v'1P'
.LP
.sp 2P
.LP
\fBRecommendation\ M.75\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBTECHNICAL\ SERVICE\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.75''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.75 %'
.ce 0
.sp 1P
.LP
\fB1\fR \fBGeneral\fR
.sp 1P
.RT
.PP
1.1
The term \*Qtechnical service\*U (sometimes \*Qtechnical
services\*U) is used throughout the Series M Recommendations. The term
is used to indicate the appropriate authorities within an Administration
which have
responsi
bility for: making international agreements on technical and
engineering aspects of provision and maintenance, allocating responsibilities
to maintenance units within the same Administration, specifying provision
and maintenance facilities, and determining provision and maintenance policy
and
overseeing its implementation. Thus it can be seen that the responsibilities
of the technical service are at a higher administrative level than those
of the
staff concerned with day\(hyto\(hyday operation of international services.
.sp 9p
.RT
.LP
.PP
1.2
The staff of the technical service is generally part of the
central headquarters of the Administration. However, Administrations sometimes
delegate some or all of their technical service responsibilities to regional
centres or even operational maintenance units. In such cases the technical
service remains responsible for ensuring that the delegated responsibilities
are satisfactorily carried out.
.bp
.sp 9p
.RT
.sp 2P
.LP
\fB2\fR \fBOutline of responsibilities\fR
.sp 1P
.RT
.PP
As far as international cooperation and coordination are concerned, the
responsibilities of the technical service
are specified in various Series M\ Recommendations. The following list,
which is not exhaustive, serves to illustrate the type of functions normally
performed by the technical service of an Administration:
.RT
.LP
\(em
making international agreements on the appointment of control
and sub\(hycontrol stations, and ensuring that the stations so
appointed are advised accordingly;
.LP
\(em
reaching international agreements on all matters relating to
the engineering provision of new and rearranged telephone
circuits, leased circuits,\ etc.; digital blocks, paths,\ etc.;
groups, supergroups,\ etc.; and so on;
.LP
\(em
exchanging contact point and other maintenance information
between Administrations;
.LP
\(em
the escalation procedure in Recommendation M.711 acting as a
centralized escalation point for those faults and problems which
cannot be cleared by staff at maintenance units, even after
discussions between the managers of such units. For example,
escalation may be required where special test equipment or
specialized expertise is needed;
.LP
\(em
ensuring the satisfactory preparation and execution of
routine maintenance schedules;
.LP
\(em
developing and keeping up to date plans for the restoration
of service in the event of the failure of international
transmission systems;
.LP
\(em
ensuring that other Administrations are advised of planned
interruptions to transmission systems in its own country, and
ensuring that steps are taken to minimize their effect on
international services.
.PP
The functions mentioned above are based on responsibilities
imposed on the technical service by Series M Recommendations.
.sp 2P
.LP
\fB3\fR \fBContact point information\fR
.sp 1P
.RT
.PP
Contact point information for the technical service should be
exchanged between Administrations in accordance with Recommendation\ M.93. If
the responsibilities of the technical service have been split on a
functional basis, contact point information for each separate function
should be exchanged. If technical service responsibilities have been delegated
(as
envisaged in \(sc\ 1.2 above), contact point information for the responsible
central headquarters staff should be exchanged.
\v'1P'
.RT
.LP
.sp 2P
.LP
\fBRecommendation\ M.80\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBCONTROL\ STATIONS\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.80''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.80 %'
.ce 0
.sp 1P
.LP
\fB1\fR \fBDefinition of control station\fR
.sp 1P
.RT
.PP
A control station is that point within the general maintenance
organization which fulfils the control responsibilities for the circuit,
group, supergroup, digital section, etc., assigned to it.
.RT
.LP
.sp 2P
.LP
\fB2\fR \fBAppointment of control stations\fR
.sp 1P
.RT
.PP
The following principles for control stations apply to:
.RT
.LP
\(em
every international circuit (circuit control station),
.LP
\(em
every international group, supergroup, digital block, digital
path, etc. (group control station, supergroup control station,
digital block control station, digital path control station,
etc.),
.LP
\(em
every line link, every regulated line section and every
digital section (line link control station, regulated line
section control station, digital section control station) using
a symmetric pair line, a coaxial line, an optical fibre or a
radio\(hyrelay link.
.bp
.sp 1P
.LP
2.1
\fICircuit control station\fR
.sp 9p
.RT
.PP
A circuit control station is nominated for each international
circuit used for public telephony or for leased or special purposes in
accordance with Recommendations\ M.723 and\ M.1012\ [1] as appropriate. In the
case of sound\(hyprogramme or television circuits, the terminal ISPC
.PP
(International Sound\(hyProgramme Centre) or ITC (International Television
Centre) at the receiving end should be nominated as the control station.
(See Recommendations\ N.1\ [2], N.5\ [3] and\ N.55\ [4].)
.RT
.sp 1P
.LP
2.2
\fIGroup, supergroup, digital block, etc. control stations\fR
.sp 9p
.RT
.PP
For each international group, supergroup, digital block, etc., the terminal
repeater station is a control station for its incoming direction of
transmission. There are thus two control stations, one for each direction
of transmission.
.RT
.sp 1P
.LP
2.3
\fIRegulated line section control station\fR
.sp 9p
.RT
.PP
The procedure is the same as for groups, supergroups, digital
blocks, etc., that is to say, each of the terminal repeater stations is a
control station for the incoming direction of transmission.
.RT
.sp 1P
.LP
2.4
\fIDigital path control station\fR
.sp 9p
.RT
.PP
For each digital path, each terminal station is a control station for its
incoming direction of transmission. There are thus two control
stations, one for each direction of transmission.
.RT
.LP
.sp 2P
.LP
\fB3\fR \fBResponsibilities of circuit control stations\fR
.sp 1P
.RT
.PP
See Recommendations\ M.723 and\ M.1012\ [1] concerning public
automatic telephone circuits, leased circuits and special circuits,
respectively. See Recommendations\ N.5\ [3] and N.55\ [4] in connection with
sound\(hyprogramme and television circuits.
.RT
.sp 2P
.LP
\fB4\fR \fBResponsibilities of control stations for groups,
supergroups, digital paths, etc.\fR
.sp 1P
.RT
.PP
4.1
Group, supergroup, digital block, digital path, regulated line section,
line link, etc. control stations are responsible for the incoming
direction of transmission only.
.sp 9p
.RT
.PP
4.2
Each control station is responsible for ensuring that the
group,
supergroup, digital block, digital path, link, line, etc. with which it is
concerned is set up and maintained to the required standards. In particular,
it is responsible for:
.sp 9p
.RT
.LP
a)
controlling lining\(hyup measurements to within the
recommended limits and keeping records of reference measurements
(initial measurements) for \fIanalogue transmission systems\fR ;
.LP
b)
ensuring that the performance of digital transmission
systems is kept within recommended limits and keeping records of
initial measurements;
.LP
c)
ensuring that routine maintenance measurements are carried
out on the due dates, using the specified methods and in such a
way that interruptions to service are limited to the shortest
possible duration;
.LP
d)
ensuring that the stations concerned take action when a
fault occurs, and controlling the various tests or
investigations necessary in clearing the fault. It must be
possible to report faults discovered at any time of the day or
night;
.LP
e)
informing the circuit control station of any condition
which might affect the operation of the circuits under its
control;
.LP
f
)
seeking the authority of the circuit control station
for any action which will take a circuit, or circuits, out of
service;
.LP
g)
knowing what are the possibilities of rerouting any faulty groups, supergroups,\
etc.;
.LP
h)
recording, on forms provided for the purpose, all incidents
which arise, giving the time of occurrence of the incident, the
exact location if known, the action taken if any, and the time of restoration
to service.
.bp
.PP
4.3
Thus, for technical purposes (maintenance, lining\(hyup) the control function
for digital paths, groups, supergroups, mastergroups,
supermastergroups and regulated line sections are divided between the two
directions of transmission, the station at the incoming end being the control
station in each case. However, it is considered desirable to have a single
routing form for each, giving information about both directions of
transmission, and in order that this and similar documentation may be prepared
and distributed on a methodical basis, these documentary functions shall
be
added to the responsibilities of one of the control stations, this
\fIcontrol station for documentary purposes\fR being chosen by agreement
between the Administrations concerned.
.LP
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fICircuit control station for leased and special\fR
\fIcircuits\fR , Vol.\ IV, Rec.\ M.1012.
.LP
[2]
CCITT Recommendation \fIDefinitions for application to international\fR
\fIsound\(hyprogramme transmissions\fR , Vol.\ IV, Rec.\ N.1.
.LP
[3]
CCITT Recommendation \fIControl and subcontrol stations for\fR
\fIsound\(hyprogramme circuits, connections, etc.\fR , Vol.\ IV, Rec.\ N.5.
.LP
[4]
CCITT Recommendation \fIOrganization, responsibilities and functions\fR
\fIof control and sub\(hycontrol ITCs and control and sub\(hycontrol stations\fR
\fIfor international television connections, links, circuits and\fR
\fIcircuit sections\fR , Vol.\ IV, Rec.\ N.55.
\v'1P'
.LP
.sp 2P
.LP
\fBRecommendation\ M.90\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBSUB\(hyCONTROL\ STATIONS\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.90''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.90 %'
.ce 0
.sp 1P
.LP
\fB1\fR \fBDefinition of sub\(hycontrol station\fR
.sp 1P
.RT
.PP
A sub\(hycontrol station is a point within the general maintenance
organization which fulfils the sub\(hycontrol responsibilities of the circuit,
group, supergroup, etc. digital section, assigned to it.
.RT
.sp 2P
.LP
\fB2\fR \fBAppointment of sub\(hycontrol stations\fR
.sp 1P
.RT
.PP
The following principles apply to:
.RT
.LP
\(em
every international circuit (circuit sub\(hycontrol station),
for whatever purpose (telephony, telegraphy, sound\(hyprogramme,
data transmission, etc.). (See in particular
.LP
Recommendations\ N.5\ [1] in connection with sound\(hyprogramme
circuits and\ N.55\ [2] in connection with television circuits);
.LP
\(em
every international digital block, digital path, group,
supergroup, mastergroup or supermastergroup (digital block
sub\(hycontrol station, digital path sub\(hycontrol station, group
sub\(hycontrol station, supergroup sub\(hycontrol station, etc.);
.LP
\(em
every line link, every regulated line section and every
digital line section (line link sub\(hycontrol station, regulated
line section sub\(hycontrol station, digital line section
sub\(hycontrol station) using a symmetric pair line, a coaxial
line, an optical fibre or a radio\(hyrelay link.
.PP
The technical service of the Administration concerned designates the station
that is to act as a sub\(hycontrol station in its country and informs the
technical service of the country responsible for the control station
accordingly.
.LP
.sp 2P
.LP
2.1
\fITerminal sub\(hycontrol stations\fR
.sp 1P
.RT
.sp 1P
.LP
2.1.1
\fITerminal sub\(hycontrol stations for circuits\fR
.sp 9p
.RT
.PP
For each circuit a terminal circuit sub\(hycontrol station is
appointed in accordance with Recommendations\ M.724 and M.1013\ [3] as
appropriate.
.PP
For unidirectional constituted circuits the terminal station at the
sending end should be the terminal circuit sub\(hycontrol station. In particular,
in the case of sound\(hyprogramme or television circuits, the terminal
ISPC
or ITC at the sending end should be the terminal sub\(hycontrol station.
(See\ Recommendations\ N.5\ [1] and\ N.55\ [2].)
.bp
.RT
.sp 1P
.LP
2.1.2
\fITerminal sub\(hycontrol stations for digital blocks, digital paths,\fR
\fIgroups, supergroups, etc.\fR
.sp 9p
.RT
.PP
At the two ends of a digital block, digital path, group,
supergroup, etc., the terminal stations are designated as terminal digital
block, digital path, group, supergroup, etc., sub\(hycontrol stations for the
direction of transmission for which they are not the digital block, digital
path, group, supergroup, etc., control station.
.RT
.LP
.sp 1P
.LP
2.1.3
\fITerminal sub\(hycontrol station for a digital section, line link or\fR
\fIa regulated line section\fR
.sp 9p
.RT
.PP
At the two ends of a digital section, line link or a regulated
line section, the terminal stations are designated as terminal digital
section, line link or regulated line section sub\(hycontrol station for the
direction of transmission for which they are not the digital section, line
link or regulated line section control station.
.RT
.sp 2P
.LP
2.2
\fIIntermediate sub\(hycontrol stations\fR
.sp 1P
.RT
.sp 1P
.LP
2.2.1
\fIIntermediate sub\(hycontrol stations for circuits\fR
.sp 9p
.RT
.PP
In transit countries in which a circuit is brought to audio
frequencies or 64\ kbit/s, etc., an intermediate circuit sub\(hycontrol
station is appointed at a suitable point for each direction of transmission.
It is left to the country concerned to choose:
.RT
.LP
\(em
where this point shall be;
.LP
\(em
whether the sub\(hycontrol functions for the two directions of
transmission are vested in one station or two stations
(see Figure\ 1/M.90);
.LP
\(em
whether, as may be desirable in the case of a large country,
each direction of transmission has more than one circuit
sub\(hycontrol station per transit country.
.LP
.rs
.sp 10P
.ad r
\fBFIGURE\ 1/M.90, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
2.2.2
\fIIntermediate sub\(hycontrol stations for paths and links\fR
.sp 9p
.RT
.PP
In general, for digital paths and analogue links, in transit
countries in which the path or link concerned appears in its characteristic
bit rate or in its basic frequency range, an intermediate sub\(hycontrol
station is appointed for each direction of transmission. The countries
concerned have the same prerogatives as those indicated above for circuits
(see \(sc\ 2.2.1 and
Figure\ 1/M.90).
.RT
.sp 1P
.LP
2.2.3
\fIIntermediate sub\(hycontrol stations for regulated line sections\fR
.sp 9p
.RT
.PP
In transit countries, a regulated line section intermediate
sub\(hycontrol station is appointed for each direction of transmission,
the same discretion as for circuits being given to the country concerned
(see \(sc\ 2.2.1
above and Figure\ 1/M.90).
.RT
.LP
.sp 1P
.LP
2.3
\fICombination of functions\fR
.sp 9p
.RT
.PP
Any, or all, of the above functions may be vested in one station, depending
on the arrangements in the country concerned.
.bp
.RT
.sp 2P
.LP
\fB3\fR \fBResponsibilities of sub\(hycontrol stations for circuits\fR
.sp 1P
.RT
.PP
See Recommendations\ M.724 and M.1013\ [3] concerning automatic
public telephone circuits, leased circuits and special circuits, respectively.
See also Recommendations\ N.5\ [1] and\ N.55\ [2] in connection with
sound\(hyprogramme and television circuits.
.RT
.sp 2P
.LP
\fB4\fR \fBResponsibilities of sub\(hycontrol stations for groups,
supergroups, digital blocks, digital paths, etc.\fR
.sp 1P
.RT
.PP
The responsibilities of sub\(hycontrol stations are, for the sections which
they control, similar to those given in Recommendation\ M.80 for control
stations, but in addition they include:
.RT
.LP
\(em
cooperating with the control stations and other sub\(hycontrol
stations in locating and clearing faults;
.LP
\(em
setting up and maintaining that part of the digital path,
group link, supergroup link, mastergroup link, or regulated line link
between the through\(hyconnection stations nearest to the two
frontiers;
.LP
\(em
seeing that the transmission on the national section with
which they are concerned is within the prescribed limits;
.LP
\(em
reporting to the control station all relevant details
concerning the location and subsequent clearance of faults;
.LP
\(em
keeping the necessary records on lining\(hyup (analogue
transmission) or initial measurements (digital transmission),
fault location and fault clearing for the section for which they
are responsible.
.PP
In addition to the above responsibilities, an intermediate
sub\(hycontrol station (in a transit country) is responsible for initiating
fault localization tests on the sections it controls in response to reports
from
other control or sub\(hycontrol stations.
.LP
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fIControl and sub\(hycontrol stations for\fR
\fIsound\(hyprogramme circuits, connections, etc.,\fR Vol.\ IV, Rec.\ N.5.
.LP
[2]
CCITT Recommendation \fIOrganization, responsibilities and functions\fR
\fIof control and sub\(hycontrol ITCs and control and sub\(hycontrol stations\fR
\fIfor international television connections, links, circuits and\fR
\fIcircuit sections\fR , Vol.\ IV, Rec.\ N.55.
.LP
[3]
CCITT Recommendation \fICircuit sub\(hycontrol station for leased and\fR
\fIspecial circuits\fR , Vol.\ IV, Rec.\ M.1013.
\v'6p'
.sp 2P
.LP
\fBRecommendation\ M.93\fR
.RT
.sp 2P
.ce 1000
\fBEXCHANGE\ OF\ CONTACT\ POINT\ INFORMATION\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.93''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.93 %'
.ce 0
.ce 1000
\fBFOR\ THE\ MAINTENANCE\ OF\ INTERNATIONAL\ SERVICES\fR
.ce 0
.sp 1P
.ce 1000
\fBAND\ THE\ INTERNATIONAL\ NETWORK\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBGeneral\fR
.sp 1P
.RT
.PP
The attention of Administrations is drawn to the need for
exchanging information about telephone numbers, telex numbers, staffing
hours,\ etc., for units involved in the maintenance of international
telecommunication services. The exchange of such information is of great
assistance to international cooperation and has an important bearing on
maintenance efficiency.
.PP
This Recommendation lists services for which information should be
exchanged. The list is not exhaustive and Administrations are asked to
consider, when intending to introduce a new service, what contact point
information will be required.
.bp
.RT
.sp 2P
.LP
\fB2\fR \fBAspects to be covered by the exchange of information\fR
.sp 1P
.RT
.sp 1P
.LP
2.1
\fITechnical service\fR
.sp 9p
.RT
.PP
The general functions and responsibilities of the \*Qtechnical
service\*U are given in Recommendation M.75.
.PP
Where technical service responsibility within an Administration has
been divided on a functional basis, contact point information relating
to each function (for example, maintenance of telephone circuits, provision
of leased circuits, exchange of information for changes in national numbering
plans and circuit order of selection) should be supplied.
.RT
.sp 1P
.LP
2.2
\fIAutomatic and semi\(hyautomatic telephone service\fR
.sp 9p
.RT
.PP
For each international centre, contact point information for each of the
maintenance elements in Recommendations\ M.715 to M.725 should be
exchanged.
.RT
.sp 1P
.LP
2.3
\fIManual telephone circuits\fR
.sp 9p
.RT
.PP
For each international centre which has responsibility for manually operated
international telephone circuits, appropriate maintenance contact
point information should be exchanged.
.RT
.sp 1P
.LP
2.4
\fIOther international services\fR
.sp 9p
.RT
.PP
Contact point information, which should at least include
information for fault reporting purposes, should be exchanged for the following
international services:
.RT
.LP
\(em
circuit\(hyswitched public data communication service;
.LP
\(em
packet\(hyswitched public data communication service;
.LP
\(em
public telegram service;
.LP
\(em
teletex service;
.LP
\(em
telex service;
.LP
\(em
public facsimile service (bureau and telefax);
.LP
\(em
store and forward facsimile switching service;
.LP
\(em
phototelegraph service.
.sp 1P
.LP
2.5
\fICommon channel signalling systems\fR
.sp 9p
.RT
.PP
For each international centre where common channel signalling is
employed, contact point information should be exchanged for the maintenance
units which have responsibility for the following:
.RT
.LP
\(em
signalling system No. 6 transfer link (Recommendation
M.760);
.LP
\(em
signalling system administrative control
(Recommendations\ M.762 and\ M.782).
.PP
Where an Administration has subdivided the maintenance functions of the
SS No.\ 6 transfer link (for example, into fault reporting, control
station,\ etc.), appropriate contact point information should be supplied.
.sp 1P
.LP
2.6
\fILeased and special circuits\fR
.sp 9p
.RT
.PP
For each international centre which has responsibility for leased and special
circuits, contact point information should be exchanged for the
following:
.RT
.LP
\(em
fault report point;
.LP
\(em
testing point;
.LP
\(em
transmission maintenance point (international line)
(Recommendation M.1014\ [1]);
.LP
\(em
circuit control/sub\(hycontrol station
(Recommendations\ M.1012\ [2] and M.1013\ [3]);
.LP
\(em
restoration point for individual circuits.
.bp
.sp 1P
.LP
2.7
\fISound programme and television\fR
.sp 9p
.RT
.PP
Contact point information for the following centres concerned with sound
and television should be exchanged:
.RT
.LP
\(em
international sound\(hyprogramme centre (ISPC)
(Recommendation\ N.1\ [4]);
.LP
\(em
international television centre (ITC)
(Recommendation\ N.51\ [5]);
.LP
\(em
programme booking centre (PBC)
(Recommendation\ D.180\ [6]).
.sp 1P
.LP
2.8
\fIGroups, supergroups, etc., digital paths and blocks and\fR
\fItransmission systems\fR
.sp 9p
.RT
.LP
.PP
For each international centre, contact point information should be exchanged
for the following:
.RT
.LP
\(em
fault report point (Recommendation\ M.130);
.LP
\(em
testing point (for routines, functional tests and fault
localization);
.LP
\(em
control/sub\(hycontrol station (Recommendations M.80 and M.90);
.LP
\(em
restoration control point (Recommendation M.725);
.LP
\(em
restoration implementation point.
.sp 1P
.LP
2.9
\fISetting\(hyup and lining\(hyup activities\fR
.sp 9p
.RT
.PP
Where staff separate from those concerned with day\(hyto\(hyday
maintenance are used for setting\(hyup and lining\(hyup new or rearranged
telephone circuits, leased circuits, groups, supergroups, etc., relevant
contact point
information should be exchanged.
.RT
.sp 2P
.LP
\fB3\fR \fBExchange and distribution of contact point information\fR
.sp 1P
.RT
.PP
Annexes A, B, C, D and E to this Recommendation contain \*Qforms\*U to
be used for the purpose of exchanging contact point information.
.PP
For convenience, the form in Annex B covers contact points for the
automatic, semi\(hyautomatic and manual telephone service, and SS No.\ 6.
.PP
Each form provides for specific telephone numbers, telex numbers and
answerback codes, together with the hours of staffing for each contact point
and the name
.FS
The name to be used is that by which the maintenance unit is known within
the Administration and should ideally be the name used by
maintenance staff when answering the telephone.
.FE
of the maintenance unit
involved. The \fIremarks\fR columns on the forms should be used to supply other
useful information, such as languages spoken, telephone number of the
supervising officer of the maintenance unit.
.PP
Each contact point is afforded two horizontal lines. If the
maintenance unit normally responsible for a particular contact point is
staffed during restricted hours only, alternative contact point information
should be supplied in the lower line for use outside those hours.
.PP
In some situations a single telephone number, telex number, etc., will
cover all contact points for, say, leased and special circuits at an
international centre. In other situations, each contact point may have
its own number. The actual arrangements will depend upon the particular
organization
existing within the Administration concerned.
.PP
Each Administration should distribute completed forms (Annexes\ A to\ E)
to all Administrations likely to have use of the contact point information
involved. Furthermore, revised issues of the forms should be distributed as
required, for example, to reflect organizational changes, because a new
international centre has been put into service.
.PP
Copies of contact point information distributed to, and received from,
other Administrations should be made readily available to all staff at
maintenance centres involved in international services or the international
network. In this way, such staff are made aware of both their own functions
and responsibilities and those of the maintenance organizations of other
Administrations.
.bp
.RT
.LP
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation M.93)
.sp 9p
.RT
.ce 0
.LP
.rs
.sp 20P
.ad r
\fBFigure A\(hy1/M.93 [T1.93], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 20P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.ce 1000
ANNEX\ B
.ce 0
.ce 1000
(to Recommendation M.93)
.sp 9p
.RT
.ce 0
.LP
.rs
.sp 47P
.ad r
\fBFigure B\(hy1/M.93 [T2.93], p. 3\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce 1000
ANNEX\ C
.ce 0
.ce 1000
(to Recommendation M.93)
.sp 9p
.RT
.ce 0
.LP
.rs
.sp 47P
.ad r
\fBFigure C\(hy1/M.93 [T3.93], p. 4 \ \ \ \ A L'ITALIENNE\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce 1000
ANNEX\ D
.ce 0
.ce 1000
(to Recommendation M.93)
.sp 9p
.RT
.ce 0
.LP
.rs
.sp 47P
.ad r
\fBFigure D\(hy1/M.93 [T4.93], p. 5 \ \ \ A L'ITALIENNE\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce 1000
ANNEX\ E
.ce 0
.ce 1000
(to Recommendation M.93)
.sp 9p
.RT
.ce 0
.LP
.rs
.sp 47P
.ad r
\fBFigure E\(hy1/M.93 [T5.93], p. 6 \ \ \ \ A L'ITALIENNE\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fITransmission maintenance point international\fR
\fIline (TMP\(hyIL)\fR , Vol.\ IV, Rec.\ M.1014.
.LP
[2]
CCITT Recommendation \fICircuit control station for leased and special\fR
\fIcircuits\fR , Vol.\ IV, Rec.\ M.1012.
.LP
[3]
CCITT Recommendation \fISub\(hycontrol station for leased and special\fR
\fIcircuits\fR , Vol.\ IV, Rec.\ M.1013.
.LP
[4]
CCITT Recommendation \fIDefinitions for application to international\fR
\fIsound\(hyprogramme transmissions\fR , Vol.\ IV, Rec.\ N.1.
.LP
[5]
CCITT Recommendation \fIDefinitions for application to international\fR
\fItelevision transmissions\fR , Vol.\ IV, Rec.\ N.51.
.LP
[6]
CCITT Recommendation \fIInternational sound\(hy and television\(hyprogramme\fR
\fItransmissions\fR , Vol.\ II, Rec.\ D.180.
\v'1P'
.LP
.sp 2P
.LP
\fBRecommendation\ M.100\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBSERVICE\ CIRCUITS\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.100''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.100 %'
.ce 0
.sp 1P
.PP
To facilitate the general maintenance of the international
telephone network, \fIservice circuits\fR should be set up as may be necessary
between relevant maintenance units taking part in the international service.
.sp 1P
.RT
.PP
For the purposes of this Recommendation, a distinction is made
between the following types of service circuit:
.LP
\(em
\fBDirect service circuit\fR : a telephone or teleprinter
(teletypewriter) service circuit serving only two stations and
linking them directly.
.LP
\fINote\fR \ \(em\ It will also be necessary to consider the
communications required by technical staff for setting up and
maintaining very long circuits routed over a number of major
systems in tandem, e.g.\ London\(emSingapore circuits. These may
require service circuits to be interconnected.
.LP
\(em
\fBOmnibus service circuit\fR (see Figure\ 1/M.100\ below): a
telephone or teleprinter (teletypewriter) service circuit
serving more than two stations connected in series, any or all
of which may make connection to the service circuit
simultaneously.
.LP
\(em
\fBMultiterminal service circuit\fR (see Figure\ 2/M.100\ below):
a telephone or teleprinter (teletypewriter) service circuit
serving more than two stations and having at least one branching
point. On each \fIbranch\fR of this circuit a certain number of
stations can be connected in series. Every station served can
enter the circuit individually.
.LP
\fINote\fR \ \(em\ Attention is drawn to the possible use of selective
signalling on omnibus and multiterminal service circuits and to
the problems that may arise in achieving the necessary stability
on such circuits.
.PP
It is recommended that for the maintenance of international
circuits:
.LP
1)
all attended stations should be connected direct to the
public telephone network;
.LP
2)
the terminal stations of an international system should be
provided with a direct telephone service circuit;
.LP
3)
terminal and intermediate stations on an international
system should be provided with an omnibus telephone service
circuit;
.LP
4)
where the provision of direct teleprinter (teletypewriter)
service circuits is impracticable or uneconomical, important
repeater stations on international routes should be provided with
international telex facilities;
.LP
The equipment of the telegraph local end used on service
telegraph circuits must be capable of transmitting and receiving
signals conforming to International Telegraph Alphabet\ No.\ 2 and
must be in accordance with the provisions of
CCITT\ Recommendations;
.LP
5)
maintenance staff responsible for international circuits
should have authority to make priority calls in the
international telephone service\ [1];
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 1/M.100 p.10\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 37P
.ad r
\fBFigure 2/M.100, p.11\fR
.sp 1P
.RT
.ad b
.RT
.LP
6)
all service circuits should in general conform to the
Recommendations of the CCITT in respect of their quality and
maintenance. However, service circuits may have a restricted
quality which must nevertheless be such as to provide efficient
communication when maintenance personnel have to use languages
other than their mother tongue;
.LP
7)
in the event of a major interruption involving service
circuits, these should be accorded priority in restoration;
.LP
8)
the terminal stations of a long international submarine
cable system should be provided with a direct teleprinter
(teletypewriter) service circuit;
.LP
9)
terminal and intermediate stations on a long international
submarine cable system should be provided with an omnibus
teleprinter (teletypewriter) service circuit.
.PP
The CCIR has issued Recommendation\ 400\(hy2 concerning
service circuits for radio\(hyrelay links. (For the convenience of readers,
this Recommendation is reproduced below. CCIR Report\ 444\ [2] also
applies.)
.bp
.LP
.sp 1P
.ce 1000
CCIR\ RECOMMENDATION\ 400\(hy2
.FS
This
Recommendation applies to radio\(hyrelay systems which will transmit at least
60\ telephone channels or a television signal and comprise two staffed
terminal stations, in which the signals are demodulated to baseand, and any
number of unstaffed intermediate stations. This Recommendation applies,
where appropriate, to trans\(hyhorizon radio\(hyrelay systems.
.FE
.ce 0
.sp 1P
.ce 1000
\fBSERVICE\ CHANNELS\ TO\ BE\ PROVIDED\ FOR\ THE\ OPERATION\fR
.ce 0
.sp 1P
.ce 1000
\fBAND\ MAINTENANCE\ OF\ RADIO\(hyRELAY\ SYSTEMS\fR
.ce 0
.sp 1P
.ce 1000
(Question 4/9, Geneva, 1982)
.sp 9p
.RT
.ce 0
.sp 1P
.ad r
(1956 | | 959 | | 963 | | 966 | | 970)
.ad b
.RT
.LP
The\ CCIR,
.sp 1P
.RT
.LP
CONSIDERING
.PP
\fIa)\fR
that service channels are required for the maintenance,
supervision and control of radio\(hyrelay systems;
.sp 9p
.RT
.PP
\fIb)\fR that if, for any reason, the radio\(hyrelay system itself fails to
function, communication between various stations along the route, and from
those stations to other points is likely to assume special importance;
.PP
\fIc)\fR that agreement is desirable on the number and function of the
service channels to facilitate the planning of radio\(hyrelay systems;
.PP
\fId)\fR that service channels will be used to provide:
.LP
\(em
omnibus voice circuits,
.LP
\(em
express voice circuits,
.LP
\(em
supervisory circuits,
.LP
\(em
control and operational circuits;
.PP
\fIe)\fR that service channels will not be connected to the public
telephone network,
.LP
UNANIMOUSLY\ RECOMMENDS
.PP
that, on international radio\(hyrelay systems:
.sp 9p
.RT
.PP
\fB1.\fR
all staffed stations should be connected directly to the public
telephone network;
.PP
\fB2.\fR
when a radio\(hyrelay link is extended by means of short cable
sections, and these cable sections and the radio\(hyrelay link taken together
constitute a regulated line section, the terminal stations of the radio\(hyrelay
link itself should have speaker circuits to the stations at the ends of
the
regulated line section;
.LP
.PP
\fB3.\fR
a telephone service channel (omnibus voice circuit) should be set up to
connect together all the stations on the system, whether staffed or not;
.PP
\fB4.\fR
a second telephone service channel (express voice circuit) should be provided
for direct telephonic communication between the staffed stations
receiving supervisory signals;
.PP
\fB5.\fR
provisions for the transmission of supervisory and control signals should
be subject to agreement between the Administrations concerned;
.PP
\fB6.\fR
the telephone service channels should possess, whenever possible, the characteristics
(excluding noise power) recommended by the CCITT for
international telephone circuits and, in particular, should be able to
transmit the frequency band 300 to 3400\ Hz;
.PP
\fB7.\fR all telephone service channels (including those used for
supervisory and control circuits) up to a length of 280\ km should, whenever
possible, not exceed a mean noise power in any hour of 20 | 00\ pW0p
psophometrically weighted, at a point of zero relative level.
.LP
\fINote\fR \ \(em\ Service channels may be provided over an auxiliary radio\(hyrelay
system, over the main radio\(hyrelay system, or by other unrelated means,
either on a primary or stand\(hyby basis. In the case of express voice
circuits, the use of regular multiplex channels within the telephony baseband
is acceptable,
where this is possible.
.bp
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT, \fIInstructions for the International Telephone Service,\fR
Articles\ 46 to\ 49, ITU, Geneva, 1985.
.LP
[2]
CCIR Report \fIService channels for analogue radio\(hyrelay systems\fR ,
Vol.\ IX, Report\ 444, ITU, Geneva, 1986.
\v'1P'
.sp 2P
.LP
\fBRecommendation\ M.110\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBCIRCUIT\ TESTING\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.110''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.110 %'
.ce 0
.sp 1P
.LP
\fB1\fR \fBAccess points for testing purposes\fR
.sp 1P
.RT
.PP
Access points are required to enable lining\(hyup and subsequent
maintenance operations to be performed on international circuits. The
required access points are as follows:
.RT
.PP
1.1
Recommendation M.565 describes and defines the access
points needed for international public telephone circuits, these points
being referred to as \*Q
circuit access points
\*U and \*Q
line access
points
\*U.
.sp 9p
.RT
.PP
Line access points and circuit access points (or appropriate means for
reaching the circuit access points) should be provided for testing all
circuits which are used for the provision of international telecommunication
services.
.PP
Where a circuit uses channel associated signalling, it should be
possible to identify and measure at the circuit access points, the
signal\(hytransmission parameters, e.g.,\ type of signal, sequence, timing,
duration, level and frequency.
.RT
.PP
1.2
Test access points
should also be provided for circuits
connected through a repeater station in transit from one country to another.
Such access points are known as \*Q
intermediate access points
\*U.
.PP
1.3
On a leased circuit, the circuit access points are regarded as
being located in the renter's premises, at the demarcation point where
connections are made to the terminal equipment used on the circuit
.FS
The
access points required for digital leased circuits have yet to be specified.
This matter is for further study by Study Group\ IV, in association with
Study Group\ XV.
.FE
.
.PP
1.4
Test access points should also be available at the terminal
international centre for circuits terminating within the country at a place
remote from the international centre, for example, in the premises of the
users of leased circuits or in a voice\(hyfrequency telegraph terminal
station, etc.
Such access points, known as line access points, should be available directly
or indirectly to the transmission maintenance point (international line)
as
defined in Recommendation\ M.1014\ [1] for such circuits.
.PP
1.5
In addition to those mentioned in \(sc\(sc\ 1.1 to 1.4 above, access
points should be provided on the audio input and output of FDM channel
multiplex and primary PCM multiplex equipments.
.PP
1.6
Access points for testing purposes should be provided on all
primary order digital paths. Such access points, known as
digital path
access points
, should be located as near to the ends of the digital path as possible.
.PP
With suitable digital test equipment, such digital path access
points enable in\(hyservice circuit monitoring to be carried out when, for
example, digital paths are directly interfaced with digital exchanges or
transmultiplexers.
.PP
When the digital path is out of service, this same point can be used to
transmit and receive signals for both digital path and circuit testing.
.RT
.PP
1.7
Figure 1/M.110 shows an example of the basic access points
for international telephone circuits terminated on an analogue exchange, and
for a variety of other telephone\(hytype circuits. Figure\ 2/M.110 shows the
basic access points for telephone circuits terminated on a digital exchange.
Figures\ 1/M.110 and 2/M.110 both show that remote access has been
provided to the \*Qcircuit access points\*U of automatic telephone circuits.
.PP
1.8
Series M Recommendations relating to the various types of
international circuits specify how the above\(hymentioned access points should
be used for line\(hyup and maintenance purposes.
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 1/M.110, p. 9\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 35P
.ad r
\fBFigure 2/M.110, p. 10\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB2\fR \fBMeasuring and testing equipment\fR
.sp 1P
.RT
.PP
2.1
The basic types of measuring equipment needed in an analogue
environment are:
.sp 9p
.RT
.LP
\(em
signal generators (fixed and variable frequency oscillators
and calibrated sending units),
.LP
\(em
level\(hymeasuring sets,
.LP
\(em
calibration units,
.LP
\(em
psophometers,
.LP
\(em
standard frequency source (or access to such a source),
.LP
\(em
equipment for signalling tests.
.PP
In addition, delay distortion measuring equipment, frequency
counters, interruption recorders, programme meters, impulsive noise counters,
phase jitter meters, automatic transmission measuring equipment, and equipment
for non\(hylinear and total distortion measurement may be required.
.bp
.PP
2.2
The basic types of test and measuring equipment needed in a
digital environment are as mentioned in \(sc\ 2.1 above. This need can
be met by
equivalent digital test/measuring equipment, or by analogue equipment and
the use of a \*Qtest coder/decoder\*U to convert digital access points
to analogue
access points. In some situations, testers for the following will prove
useful:
.sp 9p
.RT
.LP
\(em
bit error ratio;
.LP
\(em
error\(hyfree or errored seconds;
.LP
\(em
code violations;
.LP
\(em
timing jitter;
.LP
\(em
frame alignment.
.LP
.PP
2.3
The actual requirements for a particular testing centre will
depend upon the types of circuit existing at that centre, and the range of
tests and measurements that are specified for those circuits in the
relevant Series\ M Recommendations. Reference should also be made to the
\*Qfacility\*U requirements specified for the testing points defined in
Recommendations\ M.717, M.718 and M.719.
.PP
2.4
The implementation of the worldwide transmission and switching
plans makes it necessary for international circuits to be lined up and\fR
maintained to a very high degree of accuracy.
.PP
It is essential, therefore, to use measuring equipment of high
accuracy and stability in order that the maintenance requirements given
in the relevant Series M\ Recommendations for circuits are met, and to
ensure
uniformity of measurement results.
.PP
To this end it is desirable that measuring equipment provided for
lining\(hyup and maintaining all classes of circuits should, wherever possible,
conform to the measuring instrument specifications given in the Series\ O
Recommendations. Where no CCITT specification is available, the best order
of accuracy and stability should be provided, consistent with cost and
type of
measurement to be made.
.RT
.sp 2P
.LP
\fBReference\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fITransmission maintenance point international
line\fR \fI(TMP\(hyIL)\fR , Vol.\ IV, Rec.\ M.1014.
\v'1P'
.sp 2P
.LP
\fBRecommendation\ M.120\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBACCESS\ POINTS\ FOR\ MAINTENANCE\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.120''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.120 %'
.ce 0
.sp 1P
.PP
For lining\(hyup and fault localization it is proposed to define access
points at boundaries such as between switching and transmission. A
division of maintenance responsibilities can be achieved with the aid of
line access points, digital path access points and analogue link access
points. The following concepts are compatible with the division shown in
Recommendations\ Q.45 (Figure\ 1/Q.45)\ [1] and Q.502 (Figure\ 1/Q.502)\ [2].
.sp 1P
.RT
.LP
a)
A line access point separates an analogue exchange from
analogue or digital transmission [see\ a) and\ b) of
Figure\ 1/M.120].
.LP
Location and interfaces of line access points are defined in
Recommendation\ M.565.
.LP
b)
A digital path access point separates a digital exchange
from analogue or digital transmission [see\ c) and\ d) of
Figure\ 1/M.120].
.LP
Digital path access points are located at the input and
output ports of digital paths. Interfaces are defined in
Recommendation\ G.703\ [3].
.LP
c)
A line access point separates the digital exchange from the
analogue transmission [see\ e) of Figure\ 1/M.120].
.LP
d)
An analogue link access point separates a digital exchange
from an analogue transmission if line access or digital path
access is not provided. f
) of Figure\ 1/M.120 shows as an
example the collocation of a transmultiplexer with a digital
exchange.
.LP
Analogue link access points are located at the input and
output ports of analogue links. Interfaces are defined in
Recommendation\ G.233\ [4].
.PP
Normally line access points, digital path access points and
analogue link access points are provided as equipment interface,
e.g.\ accessible at distribution frames.
.bp
.LP
.rs
.sp 43P
.ad r
\fBFigure 1/M.120, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fITransmission Characteristics of an International\fR
\fIExchange\fR , Vol.\ VI, Rec.\ Q.45.
.LP
[2]
CCITT Recommendation \fIInterfaces\fR , Red Book, Vol.VI, Rec. Q.502, ITU,
Geneva, 1985.
.LP
[3]
CCITT Recommendation \fIPhysical/Electrical Characteristics of\fR
\fIHierarchical Digital Interfaces\fR , Vol.\ III, Rec.\ G.703.
.LP
[4]
CCITT Recommendation \fIRecommendations Concerning Translating Equipment\fR
, Vol\ III, Rec.\ G.233.
.bp
.sp 2P
.LP
\fBRecommendation\ M.125\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBDIGITAL\ LOOPBACK\ MECHANISMS\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.125''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.125 %'
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.LP
\fB1\fR \fBGeneral\fR
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.RT
.PP
Loopback can be one of the mechanisms which may be applied to fault localization
and failure detection. This Recommendation provides digital
loopback definitions and describes loopback applications related to the
maintenance phases of Recommendation\ M.20.
.RT
.sp 2P
.LP
\fB2\fR \fBDigital loopback definitions\fR
.sp 1P
.RT
.PP
A \fBdigital loopback\fR is a mechanism incorporated into a piece of equipment
whereby a bidirectional communication path may be connected back upon itself
so that some or all of the information contained in the bit stream sent
on the transmit path is returned on the receive path.
.PP
The \fBloopback point\fR is the location of the loopback.
.PP
The \fBloopback control mechanism\fR is the means by which the loopback
is operated and released from the loopback control point.
.PP
The \fBloopback control point\fR is the point which has the ability to
directly control loopbacks.
.PP
The loopback control point may receive requests for loopback operation
from several loopback requesting points.
.PP
The \fBloopback requesting point\fR is the point which requests the
loopback control point to operate loopbacks.
.PP
\fINote\ 1\fR \ \(em\ Loopback requests should be subject to identification
and authorization.
.PP
\fINote\ 2\fR \ \(em\ Possible locations of loopback requesting points
are: the network, or a telecommunications management network (TMN), or
a maintenance
service provider (MSP).
.PP
The \fBloopback test pattern\fR is the test information transmitted
during the operation of the loopback in the channel or channels which are
to be redirected by the loopback.
.PP
\fINote\ 1\fR \ \(em\ The generation of the test pattern used over the
loopback may or may not take place at the control point.
.PP
The \fBloopback application\fR is the maintenance phase for which the loopback
operation is used, as defined in Recommendation\ M.20.
.RT
.sp 1P
.LP
2.1
\fILoopback types\fR
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.RT
.PP
The following three types of loopback mechanisms are
defined:
.RT
.LP
a)
\fBcomplete loopback\fR \ \(em\ A complete loopback is a physical layer
[1] mechanism which operates on the full bit stream. At the loopback
point, the received bit stream shall be transmitted back towards the
transmitting station without modification.
.LP
\fINote\fR \ \(em\ The use of the term \*Qcomplete loopback\*U is not
related to implementation since such a loopback may be provided by means of
active logic elements or controlled unbalance of hybrid transformer,\ etc. At
the control point only the information channels may be available.
.LP
b)
\fBpartial loopback\fR \ \(em\ A partial loopback is a physical
layer [1] mechanism which operates on one or more specified channels
multiplexed within the full bit stream. At the loopback point, the received
bit stream associated with the specified channel(s) shall be transmitted
back
towards the transmitting station without modification.
.LP
c)
\fBlogical loopback\fR \ \(em\ A logical loopback acts selectively on
certain information within a specified channel or channels and may result
in some specified modification of the looped information. Logical loopbacks
may be defined to apply at any layer\ [1], depending on the detailed maintenance
procedures specified.
.bp
.PP
For each of the above three types of loopback mechanisms, the
loopback may be further categorized as either transparent or
non\(hytransparent:
.LP
i)
A \fBtransparent loopback\fR is one in which the signal
transmitted beyond the loopback point (the forward signal) when the loopback
is activated, is the same as the received signal at the loopback point.
See
Figure\ 1 | )/M.125.
.LP
ii)
A \fBnon\(hytransparent loopback\fR is one in which the signal transmitted
beyond the loopback point (the forward signal) when the loopback is activated
is not the same as the received signal at the loopback point. The
forward signal may be defined signal or unspecified. See
Figure\ 1 | )/M.125.
.PP
\fINote\fR \ \(em\ Whether or not a transparent loopback is used, the
loopback should not be affected by facilities connected beyond the point at
which the loop is provided, e.g.,\ by the presence of short circuits, open
circuits or foreign voltages.
.PP
Annex A to this Recommendation shows some examples of loopbacks.
.RT
.LP
.rs
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\fBFigure 1/M.125, p.\fR
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.LP
.bp
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\fB3\fR \fBLoopback applications\fR
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.RT
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3.1
\fIFailure detection\fR
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.RT
.PP
In order to detect failures related to networks maintained by
different maintenance organizations, loopbacks should be applied at the
borderline separating the maintenance responsibilities. Loopbacks should be
located in the maintenance entities (ME) adjacent to the borderline and as
close as possible to the borderline. Part of the bit stream can be involved
in failure detection. Figure\ 2/M.125 shows an example with failure detection
originated in locations\ A and\ B.
.RT
.LP
.rs
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.ad r
\fBFigure 2/M.125, p.\fR
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3.2
\fIFault localization\fR
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.RT
.PP
The localization of faults in networks consisting of \fIn\fR
maintenance entities requires at least \fIn\fR \ +\ 1 loopback mechanisms. The
loopback point should be as close as possible to the in\(hy and output ports of
the ME in order to include as much as possible of the ME in the loopback
mechanism. (See example in Figure\ 3/M.125.) Part of the bit stream or the
complete bit stream can be involved in fault localization, originated in
locations\ A or\ B.
.RT
.LP
.rs
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\fBFigure 3/M.125, p.\fR
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3.3
\fIVerification\fR
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.RT
.PP
Verification can require performance tests and measurements of the complete
bit stream.
.PP
The same loopback location can be used as for fault localization.
.RT
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.LP
\fB4\fR \fBLoopback operation and release\fR
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.RT
.PP
Loopbacks can be operated/released locally or remotely. Remote
operation/release can be based on in\(hyservice addressing (e.g.,\ layer\ 1
protocols) or it can require separate loopbacks addressing systems.
.RT
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\fB5\fR \fBLoopback examples\fR (under study \(em see Annex A)
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ANNEX\ A
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(to Recommendation M.125)
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\fBFigure A\(hy1/M.125, p.\fR
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.LP
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\fBReference\fR
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.LP
[1]
CCITT Recommendation \fIReference model of open system\fR \fIinterconnection
for CCITT applications\fR , Vol.\ VIII,
Recommendation\ X.200.
\v'1P'
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\fBRecommendation\ M.130\fR
.RT
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\fBOPERATIONAL\ PROCEDURES\ IN\ LOCATING\ AND\ CLEARING\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.130''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.130 %'
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\fBTRANSMISSION\ FAULTS\fR
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.PP
\fB1\fR
The reporting of faults on automatic circuits is dealt
with in Recommendations\ M.715 and\ M.716; for leased and special circuits in
Recommendations\ M.1012\ [1], M.1013\ [2] and M.1014\ [3] and for Signalling
System\ No.\ 6 in Recommendation\ M.762. These principles should likewise be
applied to the reporting of faults on groups, supergroups, etc.,\ to the
\fIfault report point\fR in a repeater station.
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.RT
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\fB2\fR \fBBasic principles for locating a fault on a circuit\fR
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.RT
.PP
2.1
The following principles apply to all types of circuit, however constituted:
.sp 9p
.RT
.LP
i)
The
fault report
is received by the relevant fault
report point and passed on to the circuit control station.
.LP
ii)
The circuit control station should immediately arrange for
the circuit to be withdrawn from service.
.LP
iii)
Appropriate overall measurements and tests should be made
to verify the existence of the fault.
.LP
iv)
Measurements should be made on the sections of the circuit
between the \fIend\fR of the circuit (circuit access point,
voice\(hyfrequency telegraph terminal or renter's termination,
etc.) and the international line access point at the terminal
international centre to find whether the fault is on these
sections in either of the terminal countries concerned.
.LP
v)
If the fault is proved in these sections, national practices
should be applied to locate and clear the fault.
.LP
vi)
If the fault is proved to be on the international line,
maintenance personnel at the terminal international centres
involved should make tests and measurements appropriate to the
type of fault in cooperation with any intermediate sub\(hycontrol
station until the fault has been located between two adjacent
sub\(hycontrol stations, that is, to a circuit section. These two
stations should then control the detailed location of the fault
and its subsequent clearance within their section.
.LP
\fINote\fR \ \(em\ Some types of circuit may be routed via a circuit
multiplication system (CMS). The terminal Administrations must
bilaterally agree on a detailed fault localization procedure for
circuits routed via the particular circuit multiplication system
in use between them. Annex\ A to this Recommendation contains an
outline of a fault location procedure upon which detailed
arrangements could be based.
.LP
vii)
As soon as possible, the use of any permitted rerouting
possibilities that there may be for the line or sections thereof
should be made, in order to restore service on the circuit.
.LP
viii)
If the circuit section is routed on the channel of an
FDM group or a primary digital block, the group \fIor\fR digital
block control should be informed of the fault in order to take
the necessary action.
.LP
ix)
When the fault has been cleared the sub\(hycontrol station in
whose country the fault was located should immediately notify
the control station either directly or via the appropriate
maintenance unit of the nature of the fault and the time and
details of its clearance.
.LP
x)
The controlling end should cooperate with the noncontrolling
end and should make overall measurements, requesting further
adjustments if necessary.
.LP
xi)
When the circuit meets the specified requirements, the
control station arranges to restore the circuit to
service.
.bp
.PP
2.2
Figure\ 1/M.130 shows a sequence of operations that may be
followed applying the principles given in\ \(sc\ 2.1 above.
.sp 9p
.RT
.PP
2.3
A typical sequence of operations covering transmission faults on transfer
links of Signalling System\ No.\ 6 is shown in Figure\ 2/M.760.
.sp 9p
.RT
.PP
2.4
When a fault in a circuit section is proved to be due to an
analogue group or a digital block fault, the basic fault procedures for the
group or block are the same as those given for faults on an international
line (see \(sc\ 2.1, vi and vii above).
.sp 9p
.RT
.PP
The sequence of operations followed by the group control station and the
group sub\(hycontrol station in locating faults on a group is shown in
Figure\ 2/M.130. Associated operations by other control and sub\(hycontrol
functions are shown in Figures\ 3/M.130 and\ 4/M.130.
.PP
2.5
The operations mentioned above can sometimes be modified
according
to special circumstances. For example, if there is a cable fault in a terminal
country and if this fault affects a large number of circuits, it will not
generally be necessary to carry out all the operations given in \(sc\ 2.1
above and Figure\ 1/M.130 in the order shown. (See also Supplement\ No.\
3.6\ [4])
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\fB3\fR \fBFaults observed at repeater stations as a result of local or
extended alarms\fR
.sp 1P
.RT
.PP
All fault conditions affecting transmission that are observed at
repeater stations as a result of local or extended alarms should be reported
to the relevant fault report points of the country concerned, so that
arrangements can be made to apply the fault clearing procedure.
.RT
.sp 2P
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\fB4\fR \fBSpecial faults\fR
.sp 1P
.RT
.PP
In the case of unusual faults, or faults which are difficult to
locate with the testing equipment that is available, or faults of a similar
kind occurring very frequently on a particular section, the appropriate
control station should inform its technical service without delay. This
service, in
cooperation with other technical services involved, will take the necessary
action to locate such faults or, where appropriate, prevent such faults
in the future by rearrangement of the circuit layout or equipment involved.
The
circuit control station should be kept informed of the progress of the
action taken or proposed, the prospects of clearance and other pertinent
details.
.RT
.sp 2P
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\fB5\fR \fBEscalation procedure\fR
.sp 1P
.RT
.PP
Normally cooperation between maintenance elements in different
Administrations will result in the satisfactory identification and correction
of faults. There may be circumstances, however, where the fault escalation
procedure defined in Recommendation\ M.711 may be required.
.RT
.LP
.rs
.sp 13P
.ad r
Blanc
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.LP
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.LP
.rs
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\fBFigure\ 1/M.130 p. 16\fR
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.LP
.bp
.LP
.rs
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\fBFigure\ 2/M.130 p. 17\fR
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.rs
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\fBFigure\ 3/M.130 p. 18\fR
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.bp
.LP
.rs
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\fBFigure\ 4/M.130 p. 19\fR
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.ce 1000
ANNEX\ A
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(to Recommendation M.130)
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\fBOutline procedure for
\fBlocating faults on circuits routed\fR
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\fBvia a circuit multiplication system\fR
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.PP
\fIIntroductory Notes\fR \ \(em\ In this Annex, the term, \*Qcircuit
multiplication system (CMS)\*U is used for convenience. It is intended
to cover all systems which increase the number of circuits available from
a transmission link by taking advantage of the fact that only one direction
of transmission is used at any one time in a telephone conversation (one
talker; one listener),
and that normal speech patterns involve pauses, hesitations and silent
intervals. Examples of such systems are TASI\(hyE and CELTIC.
.sp 1P
.RT
.PP
Reduced bit rate coding systems, e.g.\ transcoders, are not
presently included in the description of CMSs found in this Recommendation.
.sp 1P
.LP
A.1
\fIGeneral\fR
.sp 9p
.RT
.PP
A circuit multiplication system consists of a transmit and receive equipment
for each direction of transmission, interconnected by a number of
\*Qchannels\*U (sometimes known as connect\(hy or connection\(hychannels).
.PP
Inputs and outputs of the CMS take the form of \*Qtrunks\*U, the
number of which typically exceeds the number of channels by a factor of two.
That is, a typical CMS provides an advantage of two trunks (and
therefore, two circuits) per CMS channel.
.PP
Figure\ A\(hy1/M.130 depicts a generalized CMS, in this case interfaced
at basic circuit level. Other circuit multiplication systems are interfaced
by
primary order digital paths (operated at\ 1544 or 2048\ kbit/s) on both
trunk and channel sides of the CMS terminal equipment. Other interface
arrangements are also possible.
.PP
When the CMS is taken out of service, due to a fault or on a planned basis,
CMS trunks are switched through to CMS channels on a predetermined
basis, one trunk per channel. The circuits routed on such trunks are called
\*QCMS\(hyand\(hythrough\*U circuits
. The circuits routed on the additional
trunks derived by the CMS are called
\*QCMS\(hyonly\*U circuits
.
.RT
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A.2
\fIFault localization procedure for circuits routed via CMS\fR
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.RT
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A.2.1
\fIImpact of CMS operation\fR
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.RT
.PP
At the time a fault is detected on a circuit routed via a CMS, a
particular CMS trunk\(hyto\(hyCMS channel association existed. The fault
localization procedures must recognize that the probability of reproducing
this
trunk\(hychannel association under testing conditions is very remote, particularly
in modern circuit multiplication systems. In older systems (for example,
those interfaced at basic circuit level), there is the possibility of reproducing
the original trunk\(hychannel association, especially if both fault detection
and
testing occur during light traffic periods. This possibility should not be
overlooked in the fault localization procedures for circuits routed via such
systems.
.RT
.PP
An important feature of many modern circuit multiplication systems is that
they include self\(hydiagnostic procedures which continuously switch
trunk/channel connections even when the traffic load does not necessitate
interpolation. Such self diagnostic procedures include the monitoring of the
.PP
transmission performance of CMS channels
.FS
In some systems, minor loss
variations are also automatically compensated for.
.FE
. When pre\(hyset
thresholds (for example, of loss and noise) are exceeded, the CMS
establishes a permanent trunk/channel connection (a so\(hycalled \fR
\*Qtrunk/channel lock
\*U), and alerts maintenance staff in a suitable
manner.
.PP
To take account of these operating characteristics, the localization of
faults on circuits assigned to a CMS follows a technique that is
different from that used for normal (non\(hyCMS) circuits. Furthermore,
the test procedures to be used differ slightly depending on whether the
circuit under
test is a CMS\(hyand\(hythrough circuit or a CMS\(hyonly circuit.
.bp
.RT
.LP
.rs
.sp 27P
.ad r
\fBFigure\ A\(hy1/M.130, p. 8\fR
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.RT
.ad b
.RT
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A.2.2
\fICMS\(hyand\(hythrough circuits\fR
.sp 9p
.RT
.PP
If it is known that the CMS was out of service at the time
the circuit fault was identified, and remains out of service during fault
localization, the procedures employed for normal (non\(hyCMS) circuits can be
used.
.PP
Tests made when the CMS is in service are carried out without
regard to the CMS channel used. The existence of a fault is first verified
.PP
(or otherwise) by an initial test. If no fault is detected on the initial
test, it is safe to assume that the fault may have been due to the CMS
equipment or the interconnecting channel at the time the fault was observed.
The circuit
should be returned to service. A record of the fault should be given to the
maintenance unit responsible for the CMS for their information and use
when CMS and CMS channel tests are carried out. The fault report point
(circuit) should keep a record of the fault and the action taken for future
reference purposes.
.PP
If the fault is confirmed by the initial test and repeat tests, fault localization
procedures depend upon the particular CMS involved. In
modern systems a check should be made for the existence of a trunk/channel
lock. If such a lock exists, normal fault localization procedures used
for non\(hyCMS circuits may be used. On older systems, or if no trunk/channel
lock exists on a modern system, it can be assumed the fault is external
to the CMS and its interconnecting channels. Further tests should be made
to
identify the exact location of the fault, which should then be referred
to the appropriate maintenance unit for attention.
.PP
When localizing faults on circuits routed via older CMSs,
especially during periods of light traffic, there is a chance that the CMS
channel is faulty if identical fault conditions are observed on initial and
repeat tests \(em the CMS may not have switched channels. In this event,
further localization tests must include the CMS channel associated with the
circuit under test and the CMS terminal equipment.
.bp
.RT
.sp 1P
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A.2.3
\fICMS\(hyonly circuits\fR
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.PP
Again, tests are made on the circuit without regard to the CMS
channel being used.
.PP
The procedures for dealing with verified and unverified faults
specified in \(sc\ A.2.2 above can be used for CMS\(hyonly circuits. However,
trunk/channel locks are not generally possible on CMS\(hyonly circuits,
and thus verified faults can be assumed to be external to the CMS and its
interconnecting channels. Similar precautions to those in \(sc\ A.2.2 should be
taken when localizing faults on circuits routed via older CMSs.
.PP
When CMSs are out of service, this type of circuit is removed
from service and is not therefore available for testing purposes. Fault
localization tests must await the return to service of the CMS.
.RT
.sp 1P
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A.3
\fICMS signalling channel faults\fR
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.PP
Faults and service problems observed on circuits routed via a CMS may be
due to problems on the CMS signalling channel causing, for example,
incorrect trunk\(hychannel switching. Many CMSs monitor the performance of the
signalling channel(s) continuously. The information made available by such
monitoring should be used by maintenance staff to help eliminate signalling
channel problems as a source of circuit faults.
.RT
.sp 2P
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\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fICircuit control station for leased and special\fR
\fIcircuits\fR , Vol.\ IV, Rec.\ M.1012.
.LP
[2]
CCITT Recommendation \fISub\(hycontrol station for leased and special\fR
\fIcircuits\fR , Vol.\ IV, Rec.\ 1013.
.LP
[3]
CCITT Recommendation \fITransmission maintenance point international\fR
\fIline (TMP\(hyIL)\fR , Vol.\ IV, Rec.\ M.1014.
.LP
[4]
CCITT Supplement No. 3.6 to Volume IV \fICrosstalk test device for\fR
\fIcarrier\(hytransmission systems on coaxial systems\fR .
.LP
.rs
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\fBMONTAGE: RECOMMANDATION M.140 SUR LE RESTE DE CETTE PAGE\fR
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