Type A1961M
Intercom Amplifier

The transistorised version of the older A1961 intercom amplifier. These two amplifier types share the same enclosure and connections, and are directly swappable.

Used in multi-crew aircraft of the Cold-War era, such as Lightning T5, Vulcan and Canberra, with aircrew using dynamic microphones.

They formed the heart of intercom systems, and allowed integration with other aircraft communication and navigation systems.

It will deliver 1Watt into 10 standard UK NATO headsets / helmets connected in parallel - these are 150 ohm headsets. 2 to 20 headsets can be driven without distortion due to substantial negative feedback.

Amplifier Type A1961 front panel

The amplifier has a flat frequency response between 300Hz and 5kHz, but is sharply attenuated outside these limits.

Circuit Diagram

The input stage allows the outputs of two UHF / VHF radios (or other devices such as navigation, or warning) to be mixed with the crew microphone signals.

A1961M Intercom Amplifier circuit diagram

Power Supply

The amplifier drawings state 24Vdc supply, but most aircraft suppies are 28Vdc. This is evident in the Lightning T5 wiring diagrams:

A1961M Amplifier 28Vdc power supply from T5 Lightning wiring diagrams


NSN: 5821-99-223-7295 | Manuals: A.P.2876E, Vol.1 or A.P.116N-0105-1 | Also referred to as A.1961M


I'd quite like to find one of these amplifiers to photograph and document in detail on this site, including sound recordings to give the audio experience too. If anyone has one available, I'd be interested to talk, thanks.