TRANSMITTER-INSET No. 13

Carbon granule transmitter used in all Bakelite handsets and some early 700 type telephones.

There appears to be two variants. The Mark 1 was all metal construction (Siemens), whilst the Mark 2 had the back part moulded out of black Polystyrene (Ericsson).

Transmitter, Inset No. 13A was used in the Transmitter No. 23 and Bakelite handsets. There is no cover on this model.

Transmitter, Inset No. 13AA was used in the Transmitter No. 23A. There is no front guard cover on this variant.

Transmitter, Inset No. 13B are identifiable by a screw-nut, located on the spring plate, on the rear of the unit.

Transmitter, Inset No. 13C were of similar construction to the Transmitter, Inset No. 13B but were also supplied with a nut on a threaded pin (1/DPL/397) which was pushed into the centre hole at the rear. This version was used on 700 type telephones.

This Transmitter-Inset superseded the Transmitter-Inset No. 10 and was itself subsequently superseded by the Transmitter-Inset No. 16 for 700 type telephones.

Introduced in 1939.

Construction diagram - EX22499.

Drawing - 62808.

Specification - S133.

Ericsson Code No. N7752L (No. 13C).
STC Code No. 4025A.
Siemens Code No. A.A.100014. These were made for the Siemens/AEI Centenary Neophone and were fitted with pin type connectors only.

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