This Bakelite cased wall telephone was introduced in 1955 and used by the BPO on shared service lines.  It is fitted with an AC ringer.

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.

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.

Click here for the circuit diagram - Web users - CD users

History, Technical and General Information on 300 type telephones

Collectors information

Click here for Button labels  - Web users - CD users

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 removed and Adapter Shared-Service No. 1 fitted

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Last revised: February 09, 2018