ISLX/BTEX


PXML No. 37 & BABT/PXML/PBX.0060
APPROVAL No. DDI: NS/3343/123/J/451038, Non DDI: NS/3343/123/J/022791

See also section on BTEX 600s

The SLX is a 4 Wire Digital Switch using A-law PCM transmission.  There are 3 basic versions of the SLX each with variations according to vintage and supply source.
The SLX is approved for supply under the following versions:

Variant Brand nameBrand nameMax No Ports
SLX-MBTex400ISLX M400
SLX-SBTex600SISLX 500600
SLX-STBTex600STISLX 500600
SLX-LEBTex LEISLX LE1000
SLX-NBTex 1200DISLX 15001000
SLX-NTBTex 1200D OmegaISLX 15001000
SLX-XLBTex XL5000
SLX-XNBTex 5000DISLX 15009000
SLX-XTBTex 5000D Omega ISLX 15001000

Additionally each may be equipped with Remote Peripheral Equipment connected via 2 M-bit Private circuits or links.

The SLX-M, S and ST are single processor versions.  The other 6 types have dual processing with the off line version on hot standby.

The Systems may be either mains powered or supplied with DC from the approved battery power supply.

The system supports both Analogue and Digital PSTN trunks and DDI.  The system also supports both Analogue and Digital Private circuit and Private link Ports.

Extension telephones providing both MF and Loop disconnect dialling are supported.  There are several Feature phones and operator Consoles.

All variants of the SLX are floor standing.


The BTeX 600s replaced the BTeX-M as the single processor switch in the BT portfolio. The GPT CSL version was called the SLX-S (S for small).
The BTeX 600st is in general the same as the BTeX 600s, the only difference being that the 600st is fitted with an "OMEGA" processor.
The 600 range can be employed either as a stand-alone switch, or as a terminal node in a customer network.
The maximum capacity of the switch is limited to the six available network slots on the common equipment shelf.
BT can and does maintain both BT and GPT Communication Systems Ltd installed sites. The following is given as a comparison list.



     B.T.							GPT CSL
 SLL LE (DP)               	Equivalent                     SL1 LE
 SL1 VLE (DP)               	Equivalent                     SL1 VLE
 SL1 XL (DP)                	Equivalent                     SL1 XL
 BTeX LE (DP)               	Equivalent                     SLX LE
 BTeX XL (DP)               	Equivalent                     SLX XL
 BTeX 1200D  ("N")    (DP)   	Equivalent                     ISLX 1300
 BTeX 5000D ("XN") (DP)       	Equivalent                     ISLX 5000
 BTeX 400S  ("M")    (S)      	Equivalent                     ISLX "M"
 BTeX 600S & ST (S)           	Equivalent                     ISLX 500

DP = Dual Processors and Duplicated Memory
S = Single Processor

All systems except SL1 are "A" law PCM encoded (SL-1 uses Mu law). Internal PCM is a bit-interleaved format, not word-interleaved as in UK PCM line systems. The PABX consists of 30 channel network 'loops', each of which is normally connected to half a peripheral shelf containing up to five 16 port extension cards, or a mixture of extension and 8 port trunk cards, Traffic capacity of the switch is determined by the availability of time-slots in loops to which the ports are connected (30 conversations per loop), and the number of equipped loops.


Made by GPT Telecommunications Ltd (originally made by GEC)
Technology Drive, Beeston, Nottingham, NG9 1LA


BTEX

Introduction
The BTEX is an integrated digital PABX with the capability of switching voice and data calls.  The BTEX is manufactured by GEC Telecommunications Limited in Coventry and is marketed by British Telecom. ISLX shown to the right.

During the second half of 1987, the common equipment area of BTEX (that is CPU and network shelves) is being modified.  This modification will result in an increase in the capacity of both the LE and XL systems.

Coincident with this hardware change, will be a change in name.  The LE system will be known as the BTEX 1200 D (or N system for engineering purposes) and the XL system becomes the 5000 D (or XN for engineering purposes).

Peripheral cabinets and cards are unchanged with the new systems.

The single processor version of BTEX is the 400 S (or M system for engineering purposes).

Further changes to BTEX are being planned for the near future.  The first of these is a stand-alone ACD system using the new N processor.  The second change is a new version of the single processor M system.  This will be housed in a completely new cabinet.  Planning procedures concerning these new products will be incorporated as supplements to this guide.

Installation and maintenance of the BTEX are carried out by local area or district staff.  Sales support for BTEX is in the Business System Support Unit (BSSU) in London and Birmingham (see section 6 for addresses and telephone numbers).  The BSSU's also provide the interface for the exchange of information between districts and the contracts department of BT in the tendering and ordering of new systems or providing extensions to existing systems.

This Planning guide details all procedures and gives the necessary information to enable the customer works planner to complete the hardware order specification.

PRIVATE CIRCUIT SIGNALLING
Description By use of different trunk interface cards the BTEX can support a range of exchange and private circuit signalling systems.  Full descriptions are provided in section 1 of the System engineering handbooks.

The number and type of signalling cards has an effect on system dimensioning and quotation.  Therefore this information must be specified on the BTEX order pro-forma.

BTEX card capacities

Signalling type   Circuits per card   Card ID
AC 15 (4 wire)    4    BPC 902
DC 5 (4 wire + E and M)    4    BPC 902
DC 5 (2 wire + E and M)    4    BPC  910
DC 10 (SCDC) 2 card slots    2    BPC 909
AC 13    2    BPC 903
Paging trunk    4    BPC 910
DDI    4    BPC 910
Loop signalling    4    BPC 910
Main exchange trunk    4    BPC 908
MF5 sender/receiver    1    BPC 905
Normal extension    16    BPC 906
BTeX/SL-1 FeaturePhone    8    BPC 904
Operator's console    4    BPC 904
X21 port card    2    BPC 975
Data line card    4    BPC 912
V35 port card    4    BPC 971
Intelligent data line card    4    BPC 970
Universal digital line card    8    BPC 977

Planning details
As shown above, the line signalling cards can usually support a choice of signalling protocols.  In practice the actual signalling is determined by switch settings on the pack and the software configuration.  Hence, private circuit information must be made available to GEC for them to prepare the system data tapes properly.

MFS signalling MF5 is an advanced interregister signalling system which provides PABX facilities over a private network.  Compatibility of interworking PABXs should be considered when advising customers.  Each MF5 link will require a line signalling system (AC 15, DC5(4W) and so on) to provide supervisory conditions.  MF5 circuitry is equipped in peripheral card positions but serves a common purpose and in operation is shared between several MF5 private circuits.

Digital trunks
The digital trunks provide a 32 channel 2.048 Mb/s PCM link.  Two channels are required for signalling and frame alignment which leaves 30 speech channels (or trunks).  On LE and XL systems for each digital trunk route, one signalling card is required plus either one or two channel switch cards (one channel switch provides for a 17 Erlang route and two channel switch cards provides a 24E route).

On N and XN systems, only 24 Erlang routes are provided.  For one digital trunk route, one signalling card is required and one channel switch card (note that the channel switch provided is 2 x 24 Erlang interfaces).  Thus for two routes, two signalling cards and one channel switchcard are required.

Signalling and channel cards are situated in the network shelves in the common equipment cabinet.

Requirement
You are required to specify the number and type of signalling circuits required on the hardware order specification (apart from MF5 cards in which case GEC will calculate quantities using traffic tables). Specify in part 1 of order specification.

Action
Specify the number of digital trunks (both 17 Erlang and 24 Erlang where relevant) and the cable distance between the common equipment cabinet and the NTE (part 2).

DASS 2
Digital Access Signalling System No. 2 provides multi-line (30 channel) digital access to the public exchange (where supported by either System X or System Y).

The interface cards for DASS 2 are the same as those used for private circuit digital signalling (that is, DPNSS) and are
situated in the same shelf that is network shelves in the
common equipment cabinet.

For each DASS route, one signalling card is required, additionally a channel switch is required for each DASS route.

The capacity of the channel switch card is dependant on the system in question. (See Digital Trunks above).

For systems prior to N and XN (that is LE and XL), either one or two channel cards are required per route (one for 17 Erlang routes and two cards for 24 Erlang routes).

For N and XN systems, the channel card caters for two 24 Erlang routes.  Therefore the provision of a channel card will allow for the connection to two signalling cards.

Requirement
Specify the number of DASS 2 signalling circuits required on the hardware order specification (part 1).

Action
Specify the number of digital trunks (both DPNSS and DASS 2) and the cable distance between the common equipment cabinet and the NTE (part 2).

ATTACHMENTS/ CALL LOGGER

Description
External apparatus attached to the BTEX may be used subject

Requirement to the normal Regulatory Attachment Approval conditions.  If such a device is to be connected to the BTEX administration, maintenance, or call logging ports (the V24 port), then the device should be connected via an Attachment Interface Point.  This is commonly referred to as the CILE box.

Recommendation
Lists of approved apparatus can be obtained from the District Commercial Advisor.

Action
Check approval status of customer attachments.

BTEX-M (400 S)
Description
The BTEX-M is a single processor system and normally consists of one BCA 92 cabinet containing CPU power, tape unit and peripheral shelves.  Cabinet dimensions and weight are identical to the LE and XL systems.

The BTEX-M provides all system features and facilities that are offered by LE and XL systems, including standby power, RPE working, and DPNSS.  Software packages are identical to those of the LE and XL.

FeaturePhones

Click here for IDT400

Description
The BTEX FeaturePhone is a telephone instrument specially designed to interwork exclusively with the BTEX.  The FeaturePhone has keys which can be programmed in the BTEX software to enable the extension user to make full and rapid use of the system's facilities by simple button operation.  Instruments with a dialled number display are available, also handsfree loudspeaker units and add-on 10 or 20 way button modules.

A new basic FeaturePhone, without display and without the facility to add-on button modules, is also available.  This FeaturePhone comes in two forms, that is, non-handsfree (TX400) and the handsfree (TX410).  It uses the same line card as the original FeaturePhone.

The FeaturePhone signals digitally to the PABX line card, but voice transmission is carried in normal analogue form on separate wires.  Therefore a minimum of four wires must be provided back to the TJF for each instrument.  Power for the basic instrument is phantomed across these pairs within the PABX.  However, arrangements other than the basic instrument require supplementary power.  This can be provided locally (at the instrument using a BT transformer 17A or suitable alternative) or centrally at the PABX.  In this latter case, six wires are required between the instrument and TJF, extra power packs may be needed in the BTEX, and some jumpering will be needed on the TJF.

The FeaturePhone is fully described in sections 1 and 2 of the System engineering handbooks.  Section 2 shows allowable configurations when using local power.

The FeaturePhone requires a special interface card, the BPC 904 pack, which can support eight FeaturePhones or four attendant consoles.  Changes from ordinary phones to FeaturePhones will have to be carefully planned because the number of circuits on each normal extension interface card (BPC 906) is 16.

The auxiliary power card (BPC 913) supports eight supplies of +12v and -12v for add-on units and digit display

Recommendation
You are advised to check customer's accommodation and building wiring limitations when deciding on FeaturePhone power arrangements.

Action
Specify FeaturePhone requirements, including instruments using BT transformer 17A, on requisition A1063.

Data equipment

Descriptions
DTA, IDC
The DTA and IDC are devices which allow the customer to switch data from a V24 type interface through the PABX to another V24 device. These data ports can be given directory numbers within the PBX numbering range, and can call each other in a manner very similar to a telephony call.

The DTA is equipped with a normal telephony keypad and buttons for dialling information and call control. The IDC allows the data call routing and supervisory information to be sent from the V24 device (typically the keyboard of a VDU).

  • Both devices require only single twisted pair back to the TJF.
  • The maximum distance is 3 km.
  • The DTA requires a local power source (BT transformer 17A).
  • The IDC is mains powered.

The interface card for both the DTA and IDC is the four port data line card (BPC 912).

X21 interface
The 64 kb data line card provides for two X21 ports. This allows for nailed up circuits to be configured from the system teletype and provides point to point connections over a digital network. Wiring from the TJF to multiplex equipment must be separate from building wiring and is supplied by GEC to specified lengths. Maximum distance is 1.2 km.

V35 data module
The V35 interface module provides synchronous access through the BTEX via single twisted pairs. Calls are established by means of an autodial switch on the module.

The module connects to a four port high speed date line card (BPC 971). Maximum distance is 1.2 km. The module is mains powered.

IBM PC interface card
The PC interface card is located as a daughter board inside the PC. This enables the PC to communicate asynchronously with any compatible V24 device within a BTEX digital network.  Connections to the BTEX is via two twisted pairs to the four port IDLC card (BPC 970). Maximum distance is 1.2 km.

Asynchronous interface module (AIM)
The AIM performs a similar function to the IDC (and is similar in appearance). Unlike the IDC the AIM requires two twisted pairs back to the BTEX where the interface is the four port IDLC card/BPC 970). Maximum distance is 1.2 km. The AIM is powered by a BT transformer 17A.

Data equipment

Coax interface module (CIM)
The CIM is a desk top unit that sits adjacent to an IBM 3178 or 3278 synchronous display terminal interconnected via coax cable.  The CIM is connected on its line side, via a single twisted pair to the 14 port HSDLC card (BPC 971) on the BTEX.  Maximum distance is 1.2 km.  The module is powered by BT transformers 17A.

Multi channel coax system (MCCS)
The MCCS is the companion rack system that supports the connection (via BTEX) of up to 32 CIM'S.  The MCCS interfaces to an IBM 3274 or 3276 Cluster Controller for connection to the host computer.  Each of the 32 ports on the MCCS requires a single twisted to the BTEX where the interface card is the four port BPC 971.  Maximum distance is 1.2 km.  The system is mains powered.

Universal intelligent data connector (UIDC)
The UIDC is a data device which can be provided in different variants.  All variants interface with BTEX over single twisted pair wiring to the Universal digital line card (UDLC-BPC977).  Each UIDC requires one port of the eight port BPC977 (UDLC).  This provides two 64Kbit channels to the UIDC which itself can support V or X series interfaces.  The following UIDC variants are available:

Standalone - providing two data ports

Cluster - shelf mounted UIDC's with up to 10 per shelf, each providing two data ports

Digital FeaturePhone terminal adaptor (TA) - in this application the TA board is housed in the base of the digital FeaturePhone and supports a single data port.

Remote peripheral equipment (RPE)

Description
RPE is a facility which allows the internal BTEX multiplexed loops (two Mbit PCM highways between the common equipment and the peripheral equipment) to be extended beyond their normal 50 feet distance limit, up to a practical limit of approximately 60 km. A megastream circuit is required for each RPE loop. A maximum of four loops can be connected through two RPE shelves (one at local site and one at remote site), requiring four megastream circuits. Extra RPE shelves can be used to provide more RPE loops. The remote extensions are thereby totally integrated into the facilities and numbering plan of the main site. However, the remote extensions rely upon the integrity of the CPU at the main site and the megastream carrier for all telephony service.

Where two or more megastream circuits appear on the same cable, intermodulation distortion can occur, causing interference and loss of service.

If this situation is likely to occur on RPE installations, scrambler regenerators must be provided at the ends of the megastream circuits, located inside the line terminating equipment.

The requirements for the megastream are:

  • Maximum cable length, RPE shelf to BT Line Terminating equipment (LTE), must not exceed 6 dB which is equivalent to approximately 300 metres
  • Maximum distance between main and remote sites is limited by the maximum allowable propagation delay of the megastream circuit
  • The maximum allowable propagation delay between sites, in each direction = 0.5 ms.
  • Connection to the BTEX RPE interface at both ends is by 75 ohm BNC type co-ax connector.

BTEX 600S
One Equipment Cabinet (BCA95) which contains the following:

  • A.C. or D.C. power units
  • Common Equipment Shelf
  • Peripheral Equipment Shelf
  • Floppy Disc Unit
  • Cooling Unit
  • Transfer Units
  • Interface Assembly (power)
  • Ringer Alarm Unit

One or two Peripheral Equipment Extender Units (BCA 96) may be added, and contain the following:

Peripheral Equipment Shelf
For each Extender Unit fitted, an extra P.E. input power unit is fitted in the equipment cabinet. Extender Units are fitted on top of the Equipment Cabinet, the roof (housing the cooling unit), being fitted on top of the complete assembly. Note that the number of fans fitted in the roof increases if extender units are added.

BTEX 600S Equipment Description
P.E. and C.E. POWER UNITS.
One of each of these units is provided with one extra P.E. power unit for each Peripheral

Equipment Extender Unit fitted. The C.E. power unit provides power for the common equipment shelf and disc unit. The P.E. power unit provides power for one peripheral equipment shelf. 
Power units may be supplied for a.c. mains or for a d.c. supply (nominally - 52V) provided from a battery cabinet consisting of sealed cells and mains powered charger.

Common Equipment Shelf
The common equipment shelf consists of the following:

CENTRAL PROCESSING UNIT (C.P.U.).
The C.P.U. performs all the data manipulations and controls communication between processor, memories and input/output devices. The pack also contains one Serial Data Interface port allowing communication between the system and a teletype for maintenance and administration purposes. In addition, a built-in daughter board contains Read Only Memory (R.O.M.).

THE MISCELLANEOUS REGISTER monitors the C.P.U. operation and initiates appropriate action to maintain the system operation and generate alarms. MEMORY One Random Access Memory (R.A.M.) pack (256K max) provides storage of call processing programs and office data.

They are loaded automatically from the floppy disc on power up.

THE NETWORK PACKS provide the control signals for each traffic loop on the shelf and are interfaced by a buffer pack on Peripheral Equipment Shelves.  Single or double loop capacity Network Packs are available.

THE PERIPHERAL SIGNALLING PACK interfaces between the Network Packs and the C.P.U. for passing information to and from the C.P.U. This pack also contains the system clock.

THE CONFERENCE CARD contains a built-in dedicated network loop and provides for up to ten simultaneous three party conferences.

THE TONE AND DIGIT SWITCH generates the tones in digital PCM form and receives dialled digits.

THE MASS STORAGE INTERFACE PACK interfaces between the CPU and dual floppy disc unit.

SERIAL DATA INTERFACE PACK enables the interchange of data between the C.P.U. and data communication or terminal equipment.  The external data equipment may be a teletypewriter.  One S.D.I. pack can provide connection for two terminals.  One S.D.I. port is included on the C.P.U. circuit packs for the maintenance terminal.

DIGITAL TRUNK CHANNEL SWITCH performs system timeslot to trunk channel switching and trunk channel to system timeslot switching, and is connected to the Digital Trunk Signalling Link.

DIGITAL TRUNK SIGNALLING LINK combines speech data from the digital trunk channel switch, signalling information from the C.P.U. and frame alignment signals.  The resultant data stream is then coded for transmission over the trunk.

NOTE:  Digital trunks available on X20 release 3 for fast call set-up only.

Peripheral Equipment Each shelf contains the equipment to serve three network loops.

Shelf Each network loop can carry 15.97 Erlangs of traffic.  The base cabinet has the capacity to accommodate one P.E. shelf and therefore the capacity to serve three loops, giving a traffic capability of 3 x 15.97 = 47.91 Erlangs, at a G.O.S. of 0.01.

An additional two shelves (6 loops) can be provided giving a total traffic capability of 9 x 15.97 = 143.73 Erlangs.  This is achieved by adding two tiers (BCA 96) to the base unit.  Each tier has the capacity for 3 loops (ie one shelf).  Each loop contains seven card slots in which interface cards are fitted.  Common services such as MF4 receivers and dial tone detectors are fitted on the P.E. shelf and shared between the network loops.

The interface cards in the loop can be any combination of trunks, tie circuits or extension cards.  This allows complete flexibility when configuring the PABX to maximise its traffic handling potential.

NOTE:   The maximum number of traffic carrying network loops is 9. This is due to the physical limits of the system.

Floppy Disc Unit
A dual 5.25 inch floppy disc unit provides non-volatile storage for the system programs and configurations in case the system memory is erased during a power or control failure.

Cooling Unit
A cooling unit is provided to dissipate heat generated by shelves in the BCA 95 and BCA 96 cabinets. This is located directly above the topmost P.E. shelf, within the roof.

Transfer Units
The transfer units automatically connect preselected exchange lines to preselected standard telephones in the following circumstances:

  • the C.P.U. detects a fault with a control command that it cannot clear by internal diagnostic routines.
  • the ringer alarm unit detects a major power fault.
  • the manual transfer switch on the ringer alarm unit is operated.

Interface Assembly
The interface assembly takes input power onto the C.E. shelf from the C.E. power supply unit.

Ringer Alarm Unit
This unit provides 86V 25Hz ringing voltage and monitors system voltage levels and cabinet temperatures.  It also provides control of major and minor alarm circuits, line transfer and audible alarm indication.

System Capacity
For all cabinet options, the maximum remains the same with a total of 8 card slots which may be filled by a combination of:

  • Extra S.D.I. ports (1 card)
  • Conference Pack (1 card)
  • Single Network Pack (1 card)
  • Tone & Digit Switch (1 card)
  • Dual Network Pack (1 card)
  • Digital Trunk (DTCS & DTSL) (2 cards) (17 Erlangs) & (3 cards) (24 Erlangs)

BTEX 1200D
One Common Equipment Cabinet (BCA 92) which contains the following:

  • Rectifier shelf (240V to 50V DC)
  • Convertor shelf (DC-DC Convertor)
  • One CPU shelf
  • Two Network shelves
  • Two Peripheral shelves
  • One Disc Unit
  • Cooling Fans and Filters
  • Power Distribution Fuses and Circuit Breakers

One or two Peripheral Equipment Cabinets (BCA9 1) will be provided and contain the following:

  • Up to six Peripheral shelves
  • Convertor shelf (DC-DC convertor)
  • Rectifier shelf (240V AC to 50V DC)
  • Cooling fans and filters
  • Power distribution fuses and circuit breakers
  • Line Transfer Units or RPE shelves as required.

BTEX 1200D  The single common Equipment Cabinet BCA92 equipment

BCA92  description

CENTRAL PROCESSING UNITS (C.P.U.) There are two identical C.P.U.'s to provide hot standby working. Each consists of the following:

THE MISCELLANEOUS REGISTER monitors the C.P.U. operation and initiates appropriate action to maintain the system operation and generate alarms.

THE MASS STORAGE INTERFACE PACK interfaces between the C.P.U. and dual floppy disc unit.

MEMORY. There are two sets of memory provided, each containing identical information so as to provide hot standby working. They are loaded automatically from the floppy disc on power up.

512K RANDOM ACCESS MEMORY (RAM) cards are used to store the system configuration and call processing software.  The number of cards provided is one per C.P.U.

THE CHANGEOVER AND MEMORY ARBITRATOR (CMA) controls the changeover between C.P.U's in the event of a malfunction.  It is also capable of detecting a memory failure in RAM and specifying the use of the equivalent standby memory card without forcing a C.P.U. changeover.

NETWORK SHELVES The two network shelves provide for system security in that the 24 network traffic loops are split over two physical shelves.  Each shelf is accessed via its own 3 port Extender to guard against a shelf fault affecting the whole network group or C.P.U.

Each network shelf consists of the following:

THE NETWORK PACKS provide the control signals for each traffic loop on the shelf and are interfaced by a buffer pack on peripheral equipment shelves.

THE PERIPHERAL SIGNALLING interfaces between the network packs and the C.P.U. for passing information to and from the C.P.U.

THE TONE AND DIGIT SWITCH generates the tones in digital PCM form and receives dialled digits.

THE CONFERENCE CARD contains two built in dedicated network loops and provides for up to twenty simultaneous 3 party conferences.

THE SERIAL DATA INTERFACE (S.D.I.) contains two V24 interfaces to allow communication between the system and a teletype for maintainance and administration purposes.  An S.D.I. Port may be configured to output any combination of service change, maintenance, traffic or call information detail.  More than one S.D.I. card may be fitted.  Standard - one provision per system.

THE 3 PORT EXTENDER (3PE) allows the active C.P.U. to access each half of the network.

THE COMMON EQUIPMENT CABINET has the capacity to hold two Peripheral Shelves in the area above the C.P.U./Memory shelf.

SYNCHRONISED CLOCK GENERATOR is used in systems requiring digital networking to drive a synchronised system clock from Digital Trunk Channel Switches or other G703 compatible inputs.

DIGITAL TRUNK CHANNEL SWITCH performs system timeslot to trunk channel switching and trunk channel to system timeslot switching, and is connected to the Digital Trunk Signalling Link.

DIGITAL TRUNK SIGNALLING LINK combines speech data from the Digital Trunk Channel Switch, signalling information from the C.P.U. and frame alignment signals.  The resultant data stream is then coded for transmission over the trunk.

For peripheral equipment cabinet description see Section 3.4

NOTEThe maximum number of traffic carrying network loops is 24 which allows for redundant provisioning of the tone/digit switch and conference cards.

BTEX 5000
The BTEX 5000D system consists of two equipment cabinets, one BCA94 and one BCA93, which contain the following:

Cabinet 1 (BCA 94)

  • Two C.P.U. shelves.
  • One Memory shelf.
  • Two Network shelves (one group).
  • One disc unit.
  • Cooling Fans and Filters.
  • Power distribution fuses and Circuit Breakers.

Cabinet 2 (BCA 93)

  • Up to Six network shelves (3 additional groups).
  • Rectifier shelf (240V AC to 50V DC).
  • Converter shelf (DC-DC Converter).
  • Cooling fans and filters.

One or more Peripheral Equipment Cabinets (BCA91) will be provided and contain the following:

  • Up to six Peripheral shelves.
  • Converter Shelf (DC-DC converter).
  • Rectifier Shelf (240V AC to 50V DC).
  • Cooling fans and filters.
  • Power Distribution Fuses and Circuit Breakers.
  • Line transfer units or RPE shelves as required.

Common Equipment Description

The BCA94 serves the C.P.U./Memory and one Network group.
The BCA93 cabinet houses the equipment for three more Network groups.

BCA94 CENTRAL PROCESSING UNIT (C.P.U.)

There are two identical C.P.U.'s to provide hot standby working. Each consists of the following: 

CONTROL AND TIMING. Provides the C.P.U. with basic timing and control signals. Also performs system interrupt and C.P.U. fault monitoring.

FUNCTION BOARD. This pack contains the arithmetic logic unit (ALU) shifter, fast stack and base registers and the associated logic circuitry.

THE INTERFACE BOARD. Contains the logic required to interface the processor with the external address bus. Other bus
related circuits such as bus fault logic and Random Access
Memory (RAM) control are also included on this pack.

CONTROL, INTERFACE AND MEMORY interfaces other C.P.U. packs with common control packs. It also provides the processor with a real clock and SK of Read Only Memory (ROM) containing the initial operating instructions for the C.P.U. (Bootstrap).

THE MISCELLANEOUS CARD interfaces the processor with the external data bus. A 3-character alphanumeric display is provided to indicate system faults.

THE SEGMENTED BUS EXTENDERS (SBE) extends C.P.U. address, data and control signals between the C.P.U. and a network group shelf or a multigroup shelf. The SBE allows bus faults to be isolated to a single network group.

SYSTEM CLOCK GENERATOR. This pack provides the system clock and synchronisation facilities.

MEMORY. There are two sets of memory provided, each containing identical information so as to provide hot standby working. They are loaded automatically from the floppy disc on power up. Each memory consists of the following:

THE MASS STORAGE INTERFACE PACK interfaces between the C.P.U. and dual floppy disc unit.

512K RANDOM ACCESS MEMORY (RAM). Ram cards are provided to store the system configuration and call processing software. The number of cards provided depends on the size of the switch. 

THE CHANGEOVER AND MEMORY ARBITRATOR (CMA) controls the changeover between C.P.U.'s in the event of a malfunction.  It is also capable of detecting a memory failure in RAM and specifying the use of the equivalent standby memory card without forcing a C.P.U. changeover.

BCA 94 & BCA 93 NETWORK groups are, for security, split physically such that each network shelf contains intergroup control and switching cards to access all of the possible four network groups.

Each network shelf contains the following:

DUAL NETWORK PACKS provide the control signals for each traffic loop on the shelf, and are interfaced by a buffer pack on peripheral equipment shelves (please refer to Figs 3.3 and 3.4 on pages 3.13 and 3.14 respectively).

THE PERIPHERAL SIGNALLING interfaces between the network packs and the C.P.U. for passing information to and from the C.P.U.

THE TONE AND DIGIT SWITCH generates the tones in digital PCM form and receives dialled digits.

THE CONFERENCE CARD contains two built-in dedicated network loops and provides for up to twenty simultaneous 3-party conferences.

THE SERIAL DATA INTERFACE (S.D.I.) contains two V24 interfaces to allow communication between the system and a teletype for maintenance and administration purposes.  An S.D.I. port may be configured to output any combination of service change, maintenance, traffic or call information detail.  More than one S.D.I. card may be fitted.  Standard provision - one per system.

THE 3 PORT EXTENDER (3PE) allows the active C.P.U. to access each half of a network group.

INTERGROUP SWITCH (IGS) Provides the space switching between the four network groups.

NOTE:  The maximum number of traffic carrying loops is 136 which allows for redundant provisioning of the tone/digit switch and conference cards. 

PERIPHERAL EQUIPMENT CABINET DESCRIPTION BCA91
The Peripheral Equipment (PE) Cabinet can be considered as housing the interface equipment which allows the BTEX to communicate with the outside world. PE Cabinets are provided as necessary to accommodate the interface equipment. The PE (1200D & 5000D only) Interface Cards are terminated on a Standard Krone Distribution Frame. 

The PE Cabinet will normally contain the following:

  • 6 Peripheral Shelves
  • Fans/Filters
  • Fuse Panel and Circuit Breakers
  • Rectifier

PERIPHERAL SHELVES
Each shelf contains the equipment to serve two network loops. Each network loop can carry 17.56 Erlangs of traffic. Thus one Cabinet has the capacity to serve 12 loops and therefore a traffic capability of 12 x 17.56 = 210.72 Erlangs.

Each half shelf, serving a loop, contains seven card slots in which interface cards are fitted. Common services such as dial tone detectors and MF4 receivers are fitted on the PE Shelf and shared between the network loops.

The interface cards in the loop can be any combination of trunks, tie circuits, data cards, or extension cards. This allows complete flexibility when configuring the PABX to maximise its traffic handling potential. The following are an example of how a loop on a 1200D may be configured:

A high traffic requirement eg: a complete loop consisting of trunks at 0.7E each, would result in a maximum of 24 trunks, and with 4 circuits on a card, the shelf would be almost full with respect to traffic, although only 6 card slots would be in use on that loop.

A low traffic requirement loop of extensions each requiring 15E would allow 112 extensions which could be fitted on 7 cards.

On 1200D and 5000D systems the increased traffic capability of a network loop will in most applications allow a shelf to be fully equipped with interface cards as a mixture of cards will be provided on all loops.

The following is a list of interface card capacities/types.

FeaturePhones    8
Extensions (MF or Rotary)    16
Exchange Lines    4
AC 15/DC5    4
Loop DIS/DDI    4
Recorded Announcement    4

Peripheral Shelf Equipment may also include line transfer (Drop Back) equipment which is plate mounted with 24 circuits per plate.

Four plates can be mounted in place of one PE shelf.

Taken from BT planning manual (3/89)

 PARTS LIST
 
 
BACK Home page BT/GPO Telephones Search the Site Glossary of Telecom Terminology Quick Find All Telephone Systems

Last revised: December 21, 2010

FM