REPEATERS, TELEPHONIC No. 9A

This device was a receiving Valve amplifier, for use on customers premises, to assist persons who were hard of hearing.  Introduced in 1924, it was unpopular with users as they found it cumbersome and stigmatising.  There was a four position switch on the case for the customer to switch the apparatus on/off and also to control the volume (Direct, Medium and Max).

In 1932 the GPO Research Department concluded testing on an updated amplifier using a Mazda L.210 valve and a Candlestick telephone with a rheostat fitted in the phone.  This was the forerunner of the Repeater, Telephonic No. 17.

The Mark 5 was introduced around 1937 and was fitted with the Valve, Thermionic No. 28 or 74.

The telephone used with this amplifier was originally dependant on the exchange it was connected to.  In most cases this was a Candlestick type telephone which was later replaced by a Bakelite telephone.

The unit was powered by three "Cells, Dry Y" and a "Battery, Dry No. 2".

To be requisitioned separately:-
1 x Battery Dry No. 2.
3 x Cells, Dry Y or Cells, Leclanché DR2.
1 x Valve, Thermionic No. 28 or Valve CV 1654 or Valve CV1673.
1 x Telephone No. 144, 146, 148, or 1/194.

Superseded by Repeater, Telephonic No. 17A.

Diagram - TL 1119 (Dated 1925).
Drawing - 8238 (Mark 237).

Possibly made by GEC - click here for a GEC article

PICTURES

Picture dated 1926
The volume control switch is shown to the right
The window would have glowed when the unit was on due to light from the valve heater.

Picture dated 1926
The volume control switch is at the bottom of the photograph

Picture dated 1930
The volume control on this variant is on the top of the case
The window, by the switch, would have glowed when the unit was on due to light from the valve heater.

Picture dated 1930
 

Picture dated 1932

Last revised: November 25, 2023