TRANSMITTER,
INSETS

Early transmitter used in Telephone No. 28 and others.

Carbon granule transmitter introduced in the early 1930's and used in all bakelite handsets, later Candlesticks and some early 700 types.

Superseded by Transmitter No. 13.

Carbon granule transmitter used in all bakelite handsets and some early 700 types.

Superseded by the Transmitter Inset No. 16 for 700 type telephones.

Ericsson Code No. 7752

Click here for an article from the Ericsson Bulletin

Carbon granule transmitter used in Trimphone models and headsets.

The rubber grommet on the front is removed when used in Trimphones, but retained when used with Headset No. 1 and 2.

Carbon granule transmitter in general use from around 1960.  

Transmitter Inset No. 16 was originally fitted to all 700 type telephones.

Click here for a description of the transmitter

Superseded by Transmitter No. 21.

Superseded Transmitter Inset No. 16.  These transmitters were electronic and need line current to operate.

No. 21B was introduced at the end of 1982 and incorporated RFI suppression circuitry.