In September 1943 Auxiliary Units Special Duties requested 30 civilian type wireless receivers. It is believed that these were for use as part of the Beetle scheme, whereby messages would be broadcast to highlight a raid or invasion was underway. This had been set up in 1940, but it appears that previously Auxiliary Units had not been incorporated in the system. The sets would be kept tuned to Beetle frequency and were not to be used for any other purpose. The number suggests that one would be in use at each zero or control station.
The Murphy B81, Catalogue Number ZA 16378 to the army, was a battery powered receiver originally produced for the civilian market in 1939. It became one of two standard types used by the Army for this purpose. The other was the Murphy B93.
It has an internal aerial with a socket for an optional external one and could operate from any battery up to 109 volts and a standard 2 volt accumulator could be used. It had a black rexine covering, considered "all-weather". In October 1939 the retail price was £9 0s 0d.
Fighting Nazi Occupation, Malcolm Atkin
WO 199/936