The Med's BT Abbreviation Guide

The following is a list of abbrevations and their descriptions, the file is 
not finished in any respects and I shall be updating it in the future.. at 
the moment, in only deals with the System X switch (`SYS-X') because i don`t 
have enough infomation on AXE10 to compile much about that. 

AAR Automatic Alternative Routing. 
AAS S-X 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. 
ACP Access Control Pair. 
AEQ Automatic Announcement Equiptment. 
AIR Alarm Interface Controller 
AJG Analogue Junctions Group. 
ALE Analogue Local Exchange 
APT Alarm Port. 
ARAB TXE Alarm Reset And Busy 
ARR Automatic Re-Routing. 
ARU TXE Alarm Reporting Unit 
ASU Advanced Services Unit - FNET (Feature Net). 
ATE Automatic Telephone Exchange. 
AUS S-X Access Utility Subsystem. 
AXS Auxiliary Supervisor 
CAB Cable Box, the green things at the end of each road.. with 
everyone's lines in. 
CAS S-X 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 
CPS S-X Call Processing Subsystem 
CCR Concentrator. 
CCS Call Connect System. 
CCU Colocated Concentrator Unit. 
CCR Concentrator 
CCX Concentrator Extra Parameter 
CNI Calling Number Interception. 
COMFORTE COMputers FOR Telephone Exchanges. 
COW Clerk Of Work 
CPS S-X 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 
(0out going barred, incoming barred etc..), controls the star 
facilities, controls time outs and communicates with other 
software such as the call accounting subsystem. 
CSB Central Site Processor 
CSO Contract Supervising Officer. 
CSO Centralized Service Observation 
CSS Customer Services And Systems. 
CUG Closed User Group. 
DAM S-X Alarm Monitor 
DCD Data Compiler/Decompiler. 
DCD LOOP The process of Decompiling data and feeding the output in as the 
input to the compiler. 
DCCE S-X 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. 
DDC District Data Center 
DDT Digital Line Termination 
DDSN Digitally Derived Services Network. (0800, 0891 etc...) 
DJSU S-X 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. 
DLS S-X 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 
DLT Digital Line Termination 
DMS100 Digital Multiplexor Switch, make by AT&T Bell, and used in England 
as an International Gateway Exchange. 
DMSU S-X 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 
DPC Destination Point Code 
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 S-X Digital Switch Subsystem. The DSS carries out all the switching 
functions on a System X exchange - Trunk or local. 
DSSS S-X Digital Subscribers Switching Subsystem. See DS3. 
DSW D-Switch 
DWI Display Work Instructions - A common found trash. 
EBP Exchange Based Processor 
ECTE Exchange Terminal Computer Equiptment 
ERS Emergency Repair Service 
EL Exchange Log 
EN Equipment Number 
END Exchange name documentation 
FNET FeatureNet. 
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. 
GP Global Profile 
HTD Hardware trial period. 
I/C Incoming 
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 
procedures etc.. 
C - Listing approx 500 functions of specialisms within their 
respective main subjects. E.g Recruitment, Planning & 
Implentation etc.. 
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. 
JAX S-X Junction Circuit Auxiliary 
JCA S-X Junction Circuit Auxiliary 
JGX S-X Junction General Purpose Auxiliary 
JSW S-X Junction Q Switch 
JUN S-X Junction Subscriber 
LAN Local Area Network 
LAP Local Access Point 
LCG Line Controller Group 
LCN Line Controller Number 
LID LAN Interface Device 
LLE Large Local Exchange. 
LNE Subscriber Line 
LNO London Network Operations 
LPT Local Control Point Port 
LUN Line Unit 
MAIU Meter Alarm & Interface Unit 
MCO Maintenance Clearence Officer. OMU worked responsible for making 
sure all tasks and routines have been carried out. 
MCS S-X Maintenance Control Subsystem. Carries out maintenance functions. 
MDF Main Distribution Frame 
MED Possibly the best H^P group in the world. :) 
MEER Miscellaneous Electronic Equiptment Rack 
MFX MF4 Test Auxiliary Board 
MLE Medium Local Exchange. 
MMI Man-Machine Interface 
MMIS Man-Machine Interface Subsystem. The MMIS allows engineers to 
control and manage the exchange through VDT's etc.. 
MML Man-Machine Language 
MOJ Metering Over Junction 
MPCS Multi Party Connection Subsystem. The MPCS allows 3>10 subscribers 
to be connected together at the same time. 
MPR Microprocessor 
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 S-X 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 label, 
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. 
NAC Number Area Code 
NIC Network Interlock Code 
NSS Network Synchronisaton Facility 
O&M S-X Operations & Maintenance, look out for these (big!) folders in a 
sys-x exchange. 
O/G Outgoing 
OIM Operation & Maintenance 
OCB Outgoing Calls Barred 
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. 
OOS Out Of Service 
OUC Organisational Unit Code 
PABX Private Automatic Branch Exchange 
PACE Plessey Automatic Commisioning Equiptment 
PATE4 Print Analysis - TXE4 
PBX Private Branch Exchange 
PCM Pulse Code Modulation 
PCM links A maximum of 30 channel PCM systems coontect to the DSS which 
gives 240 speech channels (8x30) which are available to 2048 
PCS Subscriber's Private Circuit 
PDN Private Data Network 
PFT Pass Fail Thresholds 
PLEXUS/SDF Computer center with both ICL and PLEXUS systems 
PRAT Primary rate access terminal 
POE Path Of Entry 
TPOE Translation Point Of Entry 
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. 
PSN Packet Switched Network 
PSTN Public Switched Telephone Network - The standard telephone service 
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 
QSU Q-Switch 
RAD Resistance Adjustment 
RALP Remote Alarm lamp panel. 
RATES Remote Access Test Equiptment System. 
RCC Remote Concentrator Centre. Point with many RCU's. 
REMT Remote. 
RMCC S-X 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. 
RFA Ringer Fuse Alarm 
RTU Remote Terminal Unit 
SAC Service Address Code 
SADIE TXE Subscriber Automatic DIsconnect Equitment. Used to place 
subscribers apparatus TOS (Temporalily Out Of Service). 
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. 
SBR S-X ENS Exchange Subscriber 
SDP System data page 
SPM Customer's Private Meter 
SPU S-X Speech Interworking Unit. 
SIS S-X 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. 
SIU Slide-In-Unit 
STX Substitution Auxiliary 
TAC S-X Test Access Console 
TCC Through Connected Circuit . 
TE Telephone Exchange/Terminating Equipment. 
TID Terminal Identity. 
THW DSSS Test Highway 
TKO TrunK Offering 
TNC S-X Test Network Controller. 
TNET Tymnet 
TNS S-X 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. 
TOC Type Of Circuit Digits 
TOS Temporalily Out of Service 
TNC Test Network Controller 
TNO Test Network Operations 
TPN Telephony Process Number 
TSVC Telephone Service and Vechicle Centre 
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. 
3 RCU (System X) 
5 UXD5 
6-9 DLSU (System X) 
13 DMSU 
14 DJSU 
30 OSSU 
31 OCHC 
53 RSU (AXE 10 (System Y)) 
56-59 DLSU (AXE 10 (System Y)) 
80-86 OMC 
TXE Telephone eXchange Electronic.. most commonly in the form of a 
TXE4, or TXE4A (cost reduced). 
UID User Identity 
UM Unit Manager. The UM is responsible for the service given by the 
TXD exchanges in his OMC area and the organisation of staff. 
UXC Utilities Card 
UXD5 Digital Exchange developed from the CDSS1 (Monarch) PABX. 
VMB Voice Mailbox 
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. 
WN Worldwide Networks 
WNI Worldwide Networks Intstruction 
XD ExDirectory. 


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