PMBX No. 12
This Circular describes the new Premiere Call Connect System, which is now nationally
available, and details Marketing Policy, Tariff, Sales and Engineering procedures.
The Premiere Call Connect System is a prestige medium sized switchboard, designed to meet
the continuing needs of customers who prefer to have the personal service provided by a
switchboard operator. It is styled to suit contemporary office decor. The modern cordless
desk-top operator's console is push button key operated and the system equipment is
mounted on slide-in modules that are contained in a compact free standing cabinet. Direct
Outward Dialling (DOD) from extensions to the public exchange is available as an option
and automatic clearing of calls helps to reduce the operator's work load.
This is the forerunner of a new series of modular Call Connect Systems providing greater
flexibility for equipment provisioning.
The Premiere has a maximum capacity of 10 exchange lines and 48 extensions; its modular
design, based on slide-in units, allows initial requirements and subsequent growth to be
supplied in modules of 1 exchange line or 4 extensions.
Connect circuits for the connection of extension to extension calls are also provided on
slide-in "connector modules". The Premiere is equipped with a minimum of 2 such
connector modules but has capacity for a maximum of 4; if the traffic justifies a third or
fourth connector module it may be supplied and the customer will be charged accordingly.
Inter-PBX private circuits and inter-PBX extensions, up to a maximum of 4 may be provided
but their use reduces the exchange line capacity by 1 for each circuit provided. In
addition, each inter-PBX extension must be allocated an extension push button key on the
switchboard console and this reduces the extension capacity. The signalling systems
available are Manual Balanced Battery (M/BB) and Signalling System SCDC (SSDC10).
The switchboard console is a cordless light grey desk-top unit with wooden ends. It
measures 584mm wide (23 in), 255mm deep (10 in), 178mm high (7 in) and weighs 10.5kg (23
lb). All of the exchange lines, extensions and inter-PBX circuits and connect circuits
appear on push-button keys and there is a 12 push-button keypad for setting up calls over
the public network. Calls are indicated by lamps flashing inside the appropriate
push-button keys. A light-weight Trimphone handset (No. 10A), is provided for the
operator; a light weight headset (No. 1 or No. 2) may also be provided at standard
The Premiere features automatic clearing of connections and this, together with the
optional direct outward dialling facility helps to reduce the operator load and so make
the installation particularly suitable for operator/reception locations.
The associated equipment and the termination of the distribution wiring are contained
within a matching free-standing cabinet, styled to be compatible with modern office
furniture. It measures 900 mm wide (35 in), 600 m deep (23 in), 1300 mm high (51 in),
weight 200.0 kg (450 lb) fully equipped, 90.0 kg (200 lb) unequipped and is designed to be
installed in the same room as the console since the equipment is quiet in operation. The
equipment cabinet is connected to the operator's console by 2 cords, which are provided to
a standard length of 3 metres. Longer cables may be provided to meet special needs if
necessary at additional assessed charges. It may stand against a wall as maintenance
access is from the front and top covers but customers should be requested to keep the top
of the cabinet clear to permit ready access by PO staff. The system is equipped with a
combined power unit and ringing converter (No. 148A) which is housed in the bottom of the
equipment cabinet. It is operated from a 200/250v, 50 Hz supply via a 3 pin switched
socket outlet of at least 13 Amps rating which must be provided by the customer. Power
consumption does not normally exceed 3 Amps.
The equipment cabinet can be equipped with up to the following maximum quantities of
plug-in modules (Apparatus Slide-in Units ASUs):-
12 Extension Line Circuit Units (4 extensions per unit)
10 Exchange Line or Inter-PBX Circuit Units (maximum of 4 inter-PBX Circuit units)
4 Connector Units (minimum of 2 must be provided)
1 Position and Miscellaneous Circuit Unit
Other optional ASUs can be provided up to the following quantities:-
1 Predetermined Night Service Unit
1 Direct Outward Dialling (DOD) Common Control Unit
4 Direct Outward Dialling (DOD) Auxiliary Extension Line Units each providing 12 circuits
From the issue of this Circular the "PREMIERE CALL CONNECT SYSTEM is nationally
available and should be offered to:-
i. New customers with a potential requirement exceeding 4 exchange line and 18 extensions,
but not more than 10 exchange lines and 48 extensions, whose needs are best met by the
provision of a manual system.
ii. Existing customers who, upon a change of system, would fall into the category as
outlined in i. There is good potential for converting existing PMBX 10+30/10+50 customers
to the Premiere Call Connect System.
iii. Orders for supply of the Premiere Call Connect System may now be negotiated.
Engineering information to enable stores to be ordered will be avail- able from the end of
January next year but preliminary planning for accommodation and distribution wiring may
proceed with the view to bringing first installations into service as soon as practical
after receipt in areas of detailed Installation Instructions.
When discussing the Premiere Call Connect System with customers the following points
should be borne in mind:-
a. The product name of "Premiere Call Connect System', should be used in full. It
should not be reduced to initial letters.
b. The Premiere is equipped with 2 connect modules for the connecting of extension to
extension calls; these should be adequate to meet the traffic needs of most customers
having up to 24 extensions. A fully equipped system with 48 extensions is likely to
justify 4 connect modules unless, for example, the customer has a PAX catering for
extension to extension traffic. If the customer requires a traffic record the Area Traffic
Division should be consulted.
The customer should be informed that the third and fourth connect modules incur additional
c. As Direct Outward Dialling (DOD) is a major feature of the Premiere Call Connect
System, the advantages of increased efficiency and better utilisation of time by extension
users and the console operator should be fully impressed upon customers. At the same time,
the absence of operator control of extension dialled calls should be fully understood by
them. DOD may be supplied at a fixed additional charge irrespective of the number of
extensions to be so equipped. When a customer wants DOD at his installation he must decide
from which of his extensions it is to be accessed.
d. Night Service Arrangements: Consideration must be given at the outset to the
arrangements required for night service and mains failure.
e. Allocation of inter-PBX Numbers: Inter-PBX private circuits reduce the exchange line
capacity by one for each circuit provided and use either exchange line positions 10, 9, 8
or 7. In addition to the exchange line position each inter-PBX extension requires an
extension push-button key and extension numbers 48, 47, 46 and 45 must be used for this
f. Descriptive Leaflet DLC 340 is available.
Introduced in 1978.
THE PREMIERE CALL CONNECT SYSTEM
PMBX No. 12
(As this Instruction has been completely REVISED, individual paragraphs
have not been "starred".)
- ACCESS FOR REPLACEMENT ITEMS
- POWER UNIT 148A
- OFF-SITE REPAIR OF FAULTY PIUs AND SWITCHBOARDS
- ALTERATIONS TO FACILITIES
- SWITCHBOARDS SITUATED IN HIGH RISK OF LIGHTNING DAMAGE
- MAJOR SYSTEM FAILURE
- KNOWN DIFFICULTIES AND NOTES TO AID FAULTING
Premiere is a cordless system comprising a switchboard and an equipment
cubicle. The design employs sealed dry reed switching logic, with an
optimised arrangement of solid state electronics and electro-mechanical
relays for control functions. It has a maximum capacity of 10 Exchange Lines
and 48 Extensions, but up to 4 Inter PBX Private Circuits or Extensions-can
be provided by utilising spare Exchange line positions.
Additional features provided by the PMBX No. 12 are:-
- Direct Outward Dialling, which can be provided at any designated
- Automatic Call Clearing and ringing.
The Switchboard PMBX No. 12 is a cordless desk unit employing illuminated
push button keys, a Handset No. 10A-2, a Push Button Keysender, and is
supplied fully equipped.
The associated equipment cubicle, Equipment PMBX No. 12 which includes a
cross connection field can be equipped up to the following maximum
quantities of Apparatus Plug-in Units (PIUs):-
12 - Extension Line Circuits (4 Extensions per unit)
10 - Exchange Line, or Inter PBX Units
4 - Local Connector Units
1 - Position and Misc Circuit
Other optional PIUs can be provided up to the following quantities:-
1 - Predetermined Night Service Unit
1 - Direct Outward Dialling (DOD). Common Control Unit
4 - Direct Outward Dialling (DOD). Auxiliary Extension Line Units each
providing 12 circuits.
Access to the equipment cubicle is by means of the top cover (see para
6.2.1). Customers should be requested to keep the top of the cubicle clear
to permit easy access by PO staff.
A Circuit Diagram Folder (CDF 15) is provided at each installation. The
contents of the CDF are listed in Table 1. Also available to assist both
installation and maintenance engineers is an Equipment Handbook. (Customers
Apparatus Guide Notes. The Premiere Call Connect System - PMBX 12).
Other related instructions are:-
C3 E5040 - Description and Facilities
E16 A0013 - Addresses of Area Repair Centre (ARC)
El D1416 - Piece Parts
Storage space is available within the equipment cubicle to accommodate the
local records, diagrams, Equipment Handbook and small stores required for
normal maintenance e.g. Lamps, Fuses and Jumper Wire.
CONTENTS OF CDF No. 15
|FUNCTION OR TITLE
||PO DRAWING / DIAGRAM REFERENCE
|Equipment Cubicle Wiring
|Cross Connexion Diagram
|Exchange Line Connector
|Position and Misc Circuit
|Extension Line Circuit
|DOD Access Circuit
|DOD Common Control Circuit
|Manual Balanced Battery
|Operators Cordless Switchboard Cct
|Keysender No. 11A
|SS DC5 Signalling
|Limiter No. l/SA 101920
|Dial Unit SA 10204
|Power Unit No. 148A
|Operating Instruction Booklet
The design achieves high system reliability without routine attention
allowing corrective maintenance procedures to be applied. Rapid restoration
of service is aided by its modular assembly in which circuits are
accommodated in easily replaced plug in units (PIUs). Para 12 gives guidance
on known operational difficulties. In the event of a mains power failure,
all existing calls are lost and the Exchange lines are automatically
switched to the Extensions designated under Night Service 2 arrangement.
When power is restored, existing calls are maintained.
5.1 Equipment PMBX No. 12
Maintenance within the equipment cubicle will he by replacement or
transposition of the suspect PIU to indentify the faulty unit, which should
be replaced by a maintenance replacement unit. An Extractor No. 37A is
required to remove PIUs.
Faulty units should be inspected on site and repaired if appropriate e.g.
in PIUs look for pinched wires under springs, broken wires or components,
displaced 3000 Type Relay armatures and check that the Type 23 Relay
armatures are not stuck by inserting a short length of wire (18 swg), a
straightened paper clip will do, into the small hole at the back of the
relay to manually operate it.
5.2 Switchboard PMBX No. 12
Faulty lamps, key senders, buzzers, Bracket Telephone No. 19A,
Handset No. 10A-2, Telephone Unit, broken or lost
key tops can be replaced on site. However broken or faulty push button keys
should not be changed on site, but the complete switchboard replaced with a
maintenance replacement unit. An Extractor No. 4 is required to remove key
tops/lamp caps, when changing lamps.
5.2.1 Standby Dial
A standby dial is provided and should be left with the operator, or other
responsible representative of the customer, for use when required.
The Standby Dial Unit plugs into the jack situated on the base of the
switchboard adjacent to the equipment cubicle cord jacks. Plugging the unit
into this jack inhibits the self-contained keysender, the switchboard can
then be used until a replacement keysender is fitted.
The Standby Dial Unit is coded as a Dial Unit SA 10204 and comprises:-
- Dial Auto 21FA
- Mounting Dial Auto No. 22A complete Cord Instrument 5/19L, 22"
- Plug 420 Grey with Cord 1 /77AB, 54"
6 ACCESS FOR REPLACEMENT ITEMS
6.1 Switchboard PMBX No. 12
6.1.1 To change the lamps, remove the keytops/lamp caps with the
Extractor No. 4; withdraw the Lamp No. 2/6 with the Lamp Extractor No. 5.
Replace in reverse order.
6.1.2 To gain access to the Switchboard PMBX No. 12 it should first be
stood on its side and the four fixings screws situated at the corners of the
base removed to release the upper section. The two sections should then be
lowered onto the base together; the Keyboard or upper section can now be
raised independently of the base, giving access to the Keysender No. 11A,
Buzzer No. 33A and the Handset rest, Bracket Telephone No. 19A.
6.1.3 To change a Faulty Keysender No. 11A unplug the connecting cord
from the socket, release the two fixings holding the keysender and remove
the complete unit from the switchboard front panel. Fit the maintenance
replacement, using the reverse order.
6.1.4 To change the Buzzer No. 33A remove the spade-ended wiring from the
connecting screws, noting their relative positions, and unclip the faulty
buzzer. Fit the maintenance replacement using the reverse order.
6.1.5 To replace a broken handset rest (Bracket Telephone No. 19A)
release the two fixings and remove; use the reverse order to fit the
6.2 Equipment PMBX No. 12
6.2.1 To gain access to the Equipment cubicle twist the six screw
fasteners on the top panel half a turn in an anti-clockwise direction. The
top panel can then be lifted from the front and removed. This panel of the
cubicle has a diagram on the underside showing the tag block disposition and
identification. With the top panel removed, the complete cross connection
field is exposed for cabling and jumpering.
All external cabling to the equipment cubicle should be fed into either
of the side access points, but not both. This will permit access to be
gained to the back plane of the equipment rack, by turning the whole cubicle
through 90 degrees , should this be necessary.
6.2.2 Access to the PIUs and the combined power unit and ringing
converter (Power Unit No. 148A) is gained after removing the top panel (see
para 6.2.1) and then removing the front panel by releasing both locks and
gently easing the front panel forward from the top and lifting clear. Should
the rubber anti-rattle strip at the bottom of the cubicle become dislodged,
this should be replaced immediately, to prevent loss or damage, whilst
working on the equipment.
6.3 Removal and Replacement of PIUs
Use an Extractor No. 37A to remove Plug-in Units (PIUs) from the equipment
rack. A firm straight pull is required to move the PIU out approximately 10
cm (4 in). Replace the extractor into the storage place, then, using both
hands, the PIU should be completely removed taking care not to touch the
gold-plated edge contacts. When replacing the PIU, take care to ensure that
the PIU runner engages correctly in the guides, then gently slide the PIU in
until the initial resistance of the plug engaging with the socket is felt.
This occurs when the PIU front panel is approximately 1 cm (0.5 in) from its
final position. A firm push should then be given to engage the plug and
Checks to be made before inserting PIUs into the Equipment:-
- Verify that the correct PIU has been selected for insertion into the
- Check no wires are trapped in the PIU guide assemblies.
- Inspect the components and wiring to ensure that they have not been
accidentally displaced or damaged in transit.
- Check facility, or test, links are correctly located.
Damage or operational difficulties can result if any of the above checks
are not carried out.
7 POWER UNIT No. 148A
The combined power unit and ringing converter is a free standing unit
situated at the bottom of the equipment cubicle. Apart from replacement of
fuses and ensuring that the output plug is correctly inserted into the
socket, no other maintenance is required.
A Kit No. 336A containing:-
3 Fuses 72/0.25
3 Fuses 72/0.5
4 Fuses 72/3.15
is provided at each installation for maintenance purposes.
Replace faulty units with a maintenance spare.
NOTE: Before proceeding with any work on the Power Unit No. 148A switch
off the Mains Supply and isolate the unit by removing the mains plug from
8 OFF-SITE REPAIR OF FAULTY PIUs AND SWITCHBOARDS
The discrete component technology employed in the construction of PIUs
facilitates a measure of local repair. When, in the opinion of the Technical
Officer concerned with maintenance at the installation, an effective repair
can be carried out using existing off-site facilities this should be done.
This includes faulty PIUs identified by the maintenance Technician.
Otherwise faulty PIUs should be sent for repair at an Area Repair Centre.
Facilities have been made available for repair of PIUs and Switchboards
PMBX No. 12 (Cordless Desk Units) in ARCs. TI E16 A0013 gives the addresses
All faulty equipment must be packed with care in the original packing of
the replacement unit before it is returned for repair, also enclose a note
of explanation of the difficulty encountered. Include your name, address and
telephone number for the return of repaired item. A form A646 should also be
completed and forwarded via your supervising officer to the Regional Service
Group who in turn should process it appropriate manner.
The latter A646 procedure is required by the Quality Assurance Division
at present due to the suspect quality of new equipment being supplied. The
use of the form A646 for this purpose should be ceased at the end of June
1981 and the form then only used for its intended purpose i.e. Report of
Unusual Difficulty or Defect.
9 ALTERATIONS TO FACILITIES
Alterations to the following facilities may be carried out during the course
of a normal maintenance visit:-
Night Service 1
Night Service 2
Direct Outward Dialling
However the A44 procedure must be used to account the charges for the
changes and to ensure that the customers records are updated. All changes
should be entered on form A863 and a copy left with a responsible
representative of the customer.
NOTE: Night Service 2 designated extensions must be the same as those
selected for the 'Mains Fail' options.
10 SWITCHBOARDS SITUATED IN HIGH RISK AREAS OF LIGHTNING DAMAGE
Normal lightning protection is provided in accordance with TI A2 E0504. The
Position and Misc PIU has a surge limiter fitted across the -50 volt supply
rail. In areas of known high risk or sites with a previous history of
lightning damage a limiter l/SA 10192 should be fitted on all exchange line
The limiter is connected to the violet wire where this is run adjacent to
the upper frame of the PIU. The large holes are provided in the circuit
board of the limiter and these are used with suitable self tapping screws to
attach the limiter to the upper frame as near as is practicable to the PIU
back panel. (Components should face towards the PWB.)
The violet wire should be cut approximately 5 cm (2 in) from the edge
connector and both ends stripped of 2 mm (A ins) of insulation. Both ends of
the violet should be soldered to the -50 V points on the limiter, the earth
connection is made by the two self tapping screws securing the limiter to
11 MAJOR SYSTEM FAILURE
At installations where a major failure has occurred the normal operating
procedure will be to switch to the Night Service 2 option (Mains Fail) by
operating the NS2 Key on the switchboard. Exceptionally however this will
not be possible, if certain relays are being held operated by the fault
condition: under these circumstances the mains supply should be switched off
at the supply socket.
12 KNOWN DIFFICULTIES AND NOTES TO AID FAULTING
12.1 Changing Lamps Difficulty in changing switchboard lamps will be
experienced unless the correct tools are used (see Para 6.1.1).
When Connected to TXK3 or Line Finder TXS Extensions using DOD can
experience difficulty when the PMBX No. 12 is connected to a TXK3 or Line
Finder TXS type public exchanges, although calls via the switchboard
operator are satisfactory. The problem arises when a DOD extension calls the
public exchange; while waiting for dial tone the line current value can be
below that required to operate the line relay in the PMBX No. 12 exchange
line PIU so the call releases, which causes the extension to inadvertently
call the switchboard operator. This difficulty does not occur if dial tone,
and the resulting increase in line current is returned to the PMBX No. 12
within normal times of the DOD extension originating the call.
To correct this difficulty, change the line relay (LS) from a 3000 Type
Relay No. 17707 to a No. 6379.
12.3 Effects of Extension PIU Faults
A fault in an extension PIU can cause difficulty in connecting exchange
lines or local connectors to any extension telephones. First the exchange
line and then the local connector PIUs should be moved to different
positions to determine if the fault moves accordingly. If however, the fault
does not move but remains associated with the original circuit then a stuck
reed relay in an extension PIU associated with the particular circuit is the
likely cause. As the exchange line and local connectors have their cross
points in all extension PIUs the faulty PIU has to be identified and
12.4 Identifying a Faulty Extension PIU:-
- Set up a call and prove the fault condition. Clear call and press
"Release Answer" Key.
- Repeat above test with all DOD PIUs removed.
- Withdraw each extension PIU in turn repeating the test in (i) until
the faulty PIU is identified.
As all extension PIUs are identical, the remaining PIU should be
positioned to give the customer the best possible service until the faulty
PIU is replaced by a maintenance replacement unit.
12.5 Power Unit Failures
A complete system failure will occur should the Power Unit 148A fail. A
failure of the negative 50 volt can be identified by the "Green" lamp on the
switchboard being out. See Para 7. To test other outputs refer to diagram
12.6 Effects of Position and Miscellaneous PIU Failure
Failure of the Position and Miscellaneous PIU can also cause a complete
system failure. Other fault conditions that can result from failure of this
PIU are as follows:-
- No incoming signals.
- Flashing rate of incoming, and hold the signals incorrect. Possibly
the signals may be permanent or no signals depending on the mode of
- Interrupt tone too loud or not working.
- Failure to connect circuits.
- Buzzer circuit faults. (Permanent/Faint buzzer faults are usually
due to a transistor fault in other PIUs. Remove in turn all PIUs until
the faulty PIU is identified.
12.7 False Extension Call Signal on Switchboard
To prevent misoperation of the extension recall button while the handset is
on hook, from calling the switchboard operator; it is advisable to connect
the 'A' wire to Telephone T9 and the 'B' wire to Telephone T18. This is the
reverse to that shown in the telephone diagrams.
12.8 Keysender Failure
The Keysender can fail in such a way as to prevent the operator from
answering or originating exchange line calls. To overcome this difficulty a
standby dial is provided and should be plugged into the Jack situated on the
switchboard lower panel adjacent to the equipment cubicle cord jacks, this
inhibits the self-contained Keysender.
In the absence of a Standby Dial, a Plug 420 (no strapping or connections
are necessary within the plug) can be inserted into the Jack to inhibit
Keysender malfunction. The Operator can then answer incoming exchange calls,
and give extension users exchange lines to originate their own outgoing
calls until such times as the repair is effected.
12.9 No Busy Test
On restoration from night to day service or on power restoration after mains
fail, any exchange line calls in progress are held connected. If the
operator attempts to extend a further call to the extension so engaged no
busy test is given, neither is the existing call interrupted. However,
following cleardown of the call(s) in progress all functions become normal.
12.10 Access to Out of Area Lines
Out of area exchange lines may be unintentionally siezed by DOD extensions.
To overcome this difficulty complete the following modification:-
- Using a two wire jumper plus its connector join both Red and Blue
- Push connector on to tags 6-206 of exchange line jack concerned.
- Put a paper sleeve on contact spring MF6 (3000 type Relay) in
exchange line PIU.
- Label front panel of PIU for identification, and enter modification
into local records.
THE PREMIERE CALL CONNECT SYSTEM
PMBX NO. 12
- TABLE 1 - SWITCHBOARD ITEMS
- TABLE 2 - EQUIPMENT CUBICLE ITEMS
- TABLE 3 - MISCELLANEOUS ITEMS
This instruction details the piece parts that may be changed on site, and it
is essential that a supply of maintenance replacement items be available
when a PMBX No. 12 is installed. For up to the first 10 systems one set of
spares should be held. Over 10 systems a 10% holding should be maintained
for Position and Miscellaneous and DOD Common Control Plug in Units (PIUs).
The holding of all other items should be adjusted according to trend as the
number of systems increases.
Items that should not be included in the 10% spares holdings are:-
Switchboard, Equipment Cubicle and Power Unit 148A.
These items are both large and costly, and should be held on a Regional
basis. Each Regional Service Group should designate where these items and to
be kept and Area supervising officers should contact their own Regional
officer should any of these items be required.
|Bracket Telephone 19A
|Dial Unit 5A 102014 (Standby Dial)
|Handset 10A-2 complete with Plug and Cord 4/117AX
|Plug 1420 grey with cord inst 4/117AX Green 200 mm
|Headset No. 1
|Plug 420 Grey with cord 4/77AB
|Keysender No. 11A
|Key Button 3B-1 (Key Tops Blank) *
|Lamps No. 2/6v Grey
|Telephone Unit (PWB) Requires Modification
|Switchboard PMBX No. 12 (Complete)
* There are 67 differently designated Key Tops used, but for economy only
a blank is listed.
EQUIPMENT CUBICLE ITEMS
|Local Connector circuit
|Exchange Line circuit
|Position and Miscellaneous circuit
|Extension Line circuit
|Pre-determined Night Service circuit
|DOD Access circuit
|DOD Common Control circuit
|Inter PBX SCDC circuit
|Inter PBX M/BB circuit
|Equipment Cubicle PMBX No. 12 (complete with Kit 326A)
|Power Unit 148A
|Fuse No. 72/0.25
|Fuse No. 72/0.5
|Fuse No. 72/3.15
||See Table 3
|Cords Connecting No. 100/2A (Cubicle to Switchboard)
||See Table 3
|Cord Connecting No. 100/2A (Cubicle to Switchboard)
|Cords Connecting No. 100/2A - 6, 8 or 10 meter lengths
Note - These should be ordered direct from the manufacturers using the
Cable Assembly Tekdata Specification SD 4874 issue D
State length 6, 8 or 10 meters. PO description Cord Connecting 100/2A.
The Sales Manager Westport Lake
Fuse 0.55A Green - 344 CPR 100014 AAD
Fuse 1.7A Grey - 34 CPR 10004 AAC