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| PXML No. 37 & BABT/PXML/PBX.0060 APPROVAL No. DDI: NS/3343/123/J/451038, Non DDI: NS/3343/123/J/022791 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. Made by GEC.
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.
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.
BTEX Introduction 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 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:-
Planning details 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 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 Action DASS 2 The interface cards for DASS 2 are the same as those used for private circuit digital signalling (that is, DPNSS) and are 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 Action ATTACHMENTS/ CALL LOGGER Description 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 Action BTEX-M (400 S) 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 Description 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 Action Data equipment Descriptions 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).
The interface card for both the DTA and IDC is the four port data line card (BPC 912). X21 interface V35 data 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 Asynchronous interface module (AIM) Data equipment Coax interface module (CIM) Multi channel coax system (MCCS) Universal intelligent data connector (UIDC) 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 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:
BTEX 600S
One or two Peripheral Equipment Extender Units (BCA 96) may be added, and contain the following:Peripheral Equipment Shelf BTEX 600S Equipment Description 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 CENTRAL PROCESSING UNIT (C.P.U.). 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 Cooling Unit Transfer Units
Interface Assembly Ringer Alarm Unit System Capacity
BTEX 1200D
One or two Peripheral Equipment Cabinets (BCA9 1) will be provided and contain the following:
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 NOTE: The maximum number of traffic carrying network loops is 24 which allows for redundant provisioning of the tone/digit switch and conference cards. BTEX 5000 Cabinet 1 (BCA 94)
Cabinet 2 (BCA 93)
One or more Peripheral Equipment Cabinets (BCA91) will be provided and contain the following:
Common Equipment Description The BCA94 serves the C.P.U./Memory and one Network group. 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 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 PE Cabinet will normally contain the following:
PERIPHERAL SHELVES 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.
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)
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Last revised: November 05, 2021FM |
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 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.