PXML No. 83
APPROVAL No. 5/1000/2-3/C/020943

Manufactured by GEC the Senator system came as a Mark 1 or Mark 2 system and both had an ultimate configuration of 5+10. When the Merlin trading arm of BT took over marketing of business systems, the Senator Mark 2 was renamed as the S4022.

The Senator system case was wall mounted and had an integral MDF. Adaptors could be supplied to cover 2 wire external extensions, inter PBX circuits and extension bells. These adaptors would be wall mounted along side the system box. A speed dialler called the Autodial No. 5000 was introduced and this was a factory modified Tyne autodial.

The terminals used are the same ones used on the Ambassador system but the 10 memory type (Telephone No. 8550) was not sold as a Senator terminal.  These telephones are connected by four wires to the CCU and are connected via PST sockets.  The style of telephone was changed in the mid to late eighties, away from the generic Ambassador telephone style.  The later Ambassador/Senator system telephone is shown on the lower right.

LD POT phones with Earth Recall can be fitted via an External Extension Adapter ESS10253.

Senator cannot be used on PBX's which use "C" wire signalling or timed break recall.

Power consumption - 200 watts.

Sales Brochure - PH3266

Sales Brochure - PHME813

Sales Brochure - CP/MS271

See also the Ambassador system.

Go to Ambassador/Senator telephones page



Extension Socket Wiring (secondary sockets only)

System  Colour  LJU -/3A
WHITE/Blue 5
BLUE/White 2
WHITE/Orange 4
ORANGE/White 3

System Options
DPA1207A - Exchange line card (Blue handle).
DPA1209A - Extension Card (Yellow handle).
DPA1210A - LD Intercom Card to make system pulse dial (Off white handle).
DPA1217A - MF Intercom Card to make system tone dial (Grey handle).
ESS10253 - External Extension Adapter to allow connection of standard telephones.
ESS10255 - External Bell Adapter to allow connection of additional bells.

Senator ESS10253 - External extension adaptor


Senator with front cover removed

In the picture above:-
Grey handle = MF Intercom card
Blue handle = Exchange line card
Yellow handle = Extension card

CPU Card Codes
MF cards have the code 80
LD cards have the code 77/A

Fuses used on this system are BT types:- 36A/0.05, 72/0.5, 72/5, 73/0.1 & 73/4.


A problem was highlighted when engineers were experiencing difficulty with an inter PBX circuit which kept locking up between a Senator and a Pentara when calls were extended over it. The problem did not exist prior to the adaptor being changed due to a lightning strike. This was eventually cleared by changing the Senator backplane, and therefore the software, to Senator 2.

The reason for this is that all adaptors (I/C 374225) now include an additional circuit board (marked DPA1383) that replaces the original plug-in IC. This has software that offers full DC5 signalling conditions when used with Senator 2 systems but is not to be used with Senator 1. Field staff should be aware of this problem to ensure that Inter-PBX adaptors are not changed out unnecessarily.


Additional pictures
Courtesy of Yannick McCabe-Costa

Cover removed


Cards removed exposing the Backplane


Exchange Card


Extension card


MF Intercom card



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Last revised: May 15, 2023