This Bakelite cased wall telephone was introduced in 1955 and used by the BPO on shared service lines.  Produced in Automatic or C.B. variants.  The C.B. variant with fitted with a Dial, Automatic, Dummy No. 3.

It is fixed to the wall, on 4 rubber mounts, by wood screws.

It is fitted with an AC bell ringer and a single press button (no switch unit).

Produced in the colours; Black, Chinese Red, Ivory and Jade Green.

The telephone has provision for three press buttons and is used with Adaptors Shared Service No. 1 & 2.

It is the wall equivalent of Telephone No's 312, 314, 328 and 330.

The model with no press buttons was the Telephone No. 333.

Telephone No. 321F supplied by British Ericsson as their
Model No. N1075.

Telephone No. 321CB supplied by British Ericsson as their
Model No. N1423A1.

Circuit diagram - N421.

Diagram for Button labels - N620.

Drawing - 90509 (Mark 1).

History, Technical and General Information on 300 type telephones

Development of the Bakelite Wall Telephone

Collectors information

Keys for use in 300 type Wall and Table Telephones

How to wire your Telephone No. 321 to make it work on Plug and Socket

Comparison chart of GPO 300 type telephones

Case and Adapter Shared-Service No. 1 removed


Case removed exposing Adapter Shared-Service No. 1 (centre)


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Last revised: November 20, 2021