TRANSMITTER-INSET No. 10

Carbon granule transmitter introduced in the late 1920's and used in all Bakelite handsets and Candlesticks (when fitted with the Transmitter No. 22).

The mouthpiece cover of the Mark 234 was fixed by 4 screws (these were made in the GPO experimental shop).

The Mark 235 had a graphite electrode and the cover was fixed in place by a concealed spring.

Introduced in 1929 and superseded by the Transmitter-Inset No. 13 in 1939.

Non-GPO Mark 235 identification:-
Labelled 4006A - Made by TMC
Labelled Y.A. 2308 - Probably military.

Drawing - 62686 (Mark 235).

Mark 235

Last revised: June 20, 2023