Abbreviations & Descriptions
I have written the following as a guide to BT abbreviations and as a guide
to the workings of system X as it contains a lot to do with that and
various infomation which could be used at a social-engineering level, or,
if you're like me, simply intrest (or obsession??)..
AAS Automatic Announcment Subsystem. Not used in trunk exchanges
because it is done by the SIS in a trunk exchange. In a local
exchange it provides the recorded announcements (`Voice Guidance')
whilst the DS3 provides the tones.
ASU Advanced Services Network (FeatureNet)
ATE Automatic Telephone Exchange
AUS Access Utility Subsystem
CAS Call Accounting Subsystem. Uses the caller infomation to charge
the subscriber for a call and then increments the callers record
table. (the record table is a software version of the subscribers
CCS Call Connect System.
CNI Calling Number Interception
COW Clerk Of Work
CPS Call Processing Subsystem. The functions of the CPS in the local
exchange is the same as it would be on a trunk exchange. It has
overall control over any call. It registers the state of line
from the subscriber (busy/free etc..), Stores class of Service
(out going barred, incoming barred etc..), controls the star
facilities, controls time outs and communicates with other
software such as the call accounting subsystem.
CROL Cable running out list
CSO Contract Supervising Officer
CSS Customer Services And Systems
DCD Data Compiler/Decompiler
DCD LOOP The process of Decompiling data and feeding the output in as the
input to the compiler.
DCCE Digital Cell Center. This is an exchange that :
a) Provides service to its own customers and act as parent for
b) Act as a parent for analogue exchanges, terminating analogue
line plant and performing call charge as required.
c) Concentrate and foward traffic to the DMSU for parented
Analogue Local Exchanges (ALE) without their own DMSU links.
d) Switch Tandem Traffic Between other DLSUs.
DDSN Digitally Derived Services Network. (0800, 0891 etc...)
DJSU Digital Junction Switching Unit. This is a switching unit in a
high telephone density local network which performs a tandem
switching function, but has no customer connections.
DLSU Digital Local Switching Unit. General term for Digital Local
Processor Exhchange. It provides service for it's customers.
It can also provide other facilities dependaent on it's role as
either a DCCE or DLE.
DLE Digital Local Exchange. This is a DLSU which may host RCUs as in
a) for DCCEs and also act as a parent for those ALEs which will
be replaced by RSUs parented upon the DLE as in b) and c) of
DMSU Digital Main Switching Unit. Provides a fully interconencted Trunk
Network. Each DMSU catchment area will compromise of several old
GSC areas. The DMSU will switch traffic bother between and within
the catchment area.
DMU Dialled Meter Unit.
DN Directory Number
DPLE Digital Principle Local Exchange. Main exchange for an area.
DS3 Digital Subscribers Switching Subsystem. This is in principle the
same as the RCU yet it is situated inside the exchange - both are
usually called subscontractors. It is used to connect subscribers
to the local exchange. They are connected via PCM links.
DSG District Support Group (BT District Staf)
DSS Digital Switch Subsystem. The DSS carries out all the switching
functions on a System X exchange - Trunk or local.
DSSS Digital Subscribers Switching Subsystem. See DS3.
DWI Display Work Instructions - A common found trash.
ERS Emergency Repair Service
END Exchange name documentation
FMR FaultMan's Ringback. Dial the FMR (3 digit starting with 1 -
generally 17x) number and replace handset, upon ringback the
service should provide a quick analysis of any problems.
HTD Hardware trial period - minimum 5 mins
IDDF Intermediate Digital Distribution Frame
ISDN Intergrated Services Digital Network.
ISIS Inland Services Infomation System. ISIS is basically a book and
manual service. Within ISIS it is possible to find infomation
through indexing. Coding is AAA/BBB/Cxxx. AAA = Discipline,
BBB = Main Subject, C = Tertiary Function/Specialism,
xxx = document number.
AAA - listing approx 30 disciplines eg, Personal, Transmission,
Operator Services, Customer Services etc..
BBB - Listing approx 150 main subjects within the respective
disiplines eg Employment, Optical Fibre systems, Operating
C - Listing approx 500 functions of specialisms within their
respective main subjects. E.g Recruitment, Planning &
EXAMPLE = CSS/CCS/C010.. installation practice for mini master 3.
ISOS In Service Operational Support (Manufactures Staff). The ISOS
would be called in when an urgent problem needs a higher level of
support, or if a major service failure occours they can be called
in quicker than the PSG.
LLE Large Local Exchange.
MCO Maintenance Clearence Officer. OMU worked responsible for making
sure all tasks and routines have been carried out.
MCS Maintenance Control Subsystem. Carries out maintenance functions.
MLE Medium Local Exchange.
MMIS Man Machine Interface Subsystem. The MMIS allows engineers to
control and manage the exchange through VDT's etc..
MPCS Multi Party Connection Subsystem. The MPCS allows 3>10 subscribers
to be connected together at the same time.
MRA Malfunction Reporting Alarm
MSS Management Statistic Subsystem. Keeps records of the junction
routes in the local exchange and keeps traffic records for DS3s
and RCUs under it's control and also for the AAS.
MTS Message Transmission Subsystem. Terminal part of CCS (not to be
confused with CSS) link. It transmits and recieves messages sent
between distanct CPSs (Call Processing Subsystems) and carriers
out error checks on messages and re-transmits if necessary.
MTS MsgFor The MTS message format is : - Error Check, Message, Routing
header. The header contains the message number incase a resend is
needed, the routing label includes the OPC (Originating Point
Code) which identifys the originating exchange and the
Destination Point Code (DPE) which identifies the destination
exchange. The message tells CPS what it has to do and the error
check obviously checks the message for errors.
NSS Network Synchronisaton Facility
OIM Operation & Maintenance
OMC Operations & Maintenance Center. BT policy requires this, collects
data from exchanges and monitors data for presentation for the
OMC staff (Traffic, Sales, Operation & Maintenance Unit. (OMU) )
OMU Operation and Maintenance Unit. Room where engineers moniter the
performance of the exchanges, and recieve data collected my the
OMC. There is one or more connected to each OMC. OMU staff can
send data to the OMC to control the exchanges conneted to it.
PABX Private Automatic Branch Exchange
PACE Plessey Automatic Commisioning Equiptment
PBX Private Branch Exchange
PCM links A maximum of 30 channel PCM systems coontect to the DSS which
gives 240 speech channels (8x30) which are available to 2048
PLEXUS/SDF Computer center with both ICL and PLEXUS systems
PRAT Primary rate access terminal
PSG Product Support Group (BT Headquarters Staff). PSGs can be called
in if there is a problem on site. They give the authority for any
emergency design modifications carried out without authority
having being gained in advance.
PSU Power Supply Unit
PUS2 The Central Processor which provideds the processing power and
storage facilites for all other subsystems.
PXSM Pre-Extension Site meeting
RALP Remote Alarm lamp panel
RCC Remote Concentrator Centre. Point with many RCU's.
RMCC Remote Multi-Concentrator Unit. Two or more subscribers connected
in a RCC.
RCU Remote Concentrator Units. These must be connected to the DLSU and
are considered as part of the DLSU to which they are connected.
The RCU is situated away from the Telecom building in a more
convienient place and it is the apparatus that divides the lines
and gives them their equiptment numbers. If there is no
connection between the RSU and the exchange then customers may
still call numbers controlled by the RSU but not outside. Charge
Handling is handled at the TE so if there is no connection to
the TE there is no call charge. Telecom uses a standard two RCUs
for security reasons.
SALT Subscribers Automatic Line Testing. For System X and Y exchanges.
The code for this is generally 175 and has the same job as the
FaultsMans Ringback but is more advanced with increased options
after the ringback.
SDP System data page
SPM Customer's Private Meter
SIS Signalling Interworking Subsystem. Used as an interface between a
system X exchange and analogue exchanges. It convers analogue to
30 channel PCM for connection to the DSS. In like local exchange,
unlike to trunk exchange it does not send tones or annoucments -
the AAS does.
TE Telephone Exchange/Terminating Equiptment
TNS Test Network Subsystem. The TNS controls the accessing of and
testing of all digital and analogue junctions and subcriber lines.
It uses SIS to access analogue junction lines, DSS to access
digital junctions and DS3 tto access subscribers lines.
TXD #'s A method of labeling types of exchange by number that forms part
of the exchange's Network Nodal Identity which appears on all
documents specific to the particular exchange.
TXD NO EXCHANGE
3 RCU (System X)
6-9 DLSU (System X)
53 RSU (AXE 10)
56-59 DLSU (AXE 10)
UM Unit Manager. The UM is responsible for the service given by the
TXD exchanges in his OMC area and the organisation of staff.
UXD5 Digital Exchange developed from the CDSS1 (Monarch) PABX.
VRS Voice Response System. Allows remote testing of subscriber's
line gived number and code. There are possibly other
systems under the heading VMS because it's not exactly
very use specific.
WMS Work Manager System. Used by BT engineers to download their
infomation for jobs of the day. Generally used via a portable
field terminal and acostic coupler. It is accessable from any
termination point in England.
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