This Bakelite cased wall telephone was introduced in 1955.  These were used by the BPO on shared service lines and extension plans, where a wall telephone was required. 

Produced in Automatic or C.B. variants.  The C.B. variant was fitted with a Dial, Automatic, Dummy No. 3.

All components and the case are mounted on a plate.  This plate is fixed to the wall, by means of 4 rubber mounts, using wood screws.

The case was fixed by a single screw next to the Handset cord entry.  The case had a strap that was fixed to the back plate allowing the case to hang during maintenance work.

To remove the case, release the lower fixing screw adjacent t to the handset cord entry point.  Pull the bottom of the case outwards about one inch.  Lift the case upwards to release the top fixings.

It is fitted with an AC bell ringer and has provision for three press button keys.  It is supplied ready for a single press button key but has no switch unit fitted.

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.

Telephone Includes (1955):-
1 x Bell No. 59A, Unmounted.
1 x Bell-gong No. 2.
1 x Bell-gong No. 2A Nickeled.
1 x Coil, Induction No. 27.
1 x Condenser, M.C. No. 97.
1 x Cord, Instrument No. 5/28E, 5" (for Dials, Automatic only).
1 x Dial, Automatic S.S., No. 12LA & FA ... or Dummy No. 3 (Colour).
1 x Part No. 1/DCA/89 (Colour).
2 x 1/DBU/11 (Colour).
1 x Telephone No. 164 (Colour).

Circuit diagram - N421.

Diagram for Button labels - N620.

Drawing - 90509.

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

Dismantling the Handset

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

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: April 23, 2022