Air Ministry item

[Burney Davis]

Can anyone identify this item? It appears to be a clock in a heavily padded box. The closing clasps have the Air Ministry symbol on then but there is no date or other marks on the piece itself other than what can be seen in the pictures. There are two holes on each vertical surface of the box - perhaps aircraft mounted? Any information greatly appreciated.

 

[LCplCombat]

10H is RAF stores code for Radio Connectors

 

[TimG]

Master Contactor Type? 10A/10994

This clockwork mechanism was located behind the pilot's seat in the aircraft. The box interior is padded with chamois leather and there is a small heating element in the movement to aid in maintaining a constant temperature to aid accurate timekeeping. This mechanism was connected to an on-off switch in the cockpit. Before take-off, the clocks would be synchronised with the clock in the control room.
The following text kindly provided by:-
Peter Elliott
Senior Keeper
Department of Research & Information Services
Royal Air Force Museum
Hendon
“Just prior to the Second World War it was realised that there would be a need to keep track of an aircraft’s location. This led to a radio location system using an aircraft’s radio transmission which could be triangulated in ground radio stations to deduce the aircraft’s position, the system being known as ‘ [Radio] Direction Finding’. The given location was then passed on to the relevant Operations Room. Of course it was realised that if an aircraft (either on its own or as the ‘designated transmitter’ in a formation) continually transmitted then only one aircraft could be tracked on a given radio frequency, hence the contactor. This enabled a timed transmission of fourteen seconds to be made every minute, by staggering the transmissions up to four aircraft (or formations) could be tracked on one frequency, with a gap of one second between each transmission.”
PIPSQUEAK centred on a Master Contactor, incorporating a “spring-driven clock the escapement of which beats twice per second. Each vibration … closes an electrical contact, which in turn transmits an electrical impulse to the remote contactor.” The remote contactor contains a motor-driven rotor, rotating once per minute. “During 14 seconds of each minute, the rotor causes the closure of an electrical contact and consequent completion of…” the circuit which includes the operating coils of the frequency-shifting relays.” The remote contactor would be mounted in the cockpit and operated by the pilot.

TimG

 

[Burney Davis]

Master Contactor Type? 10A/10994

This clockwork mechanism was located behind the pilot's seat in the aircraft. The box interior is padded with chamois leather and there is a small heating element in the movement to aid in maintaining a constant temperature to aid accurate timekeeping. This mechanism was connected to an on-off switch in the cockpit. Before take-off, the clocks would be synchronised with the clock in the control room.
The following text kindly provided by:-
Peter Elliott
Senior Keeper
Department of Research & Information Services
Royal Air Force Museum
Hendon
“Just prior to the Second World War it was realised that there would be a need to keep track of an aircraft’s location. This led to a radio location system using an aircraft’s radio transmission which could be triangulated in ground radio stations to deduce the aircraft’s position, the system being known as ‘ [Radio] Direction Finding’. The given location was then passed on to the relevant Operations Room. Of course it was realised that if an aircraft (either on its own or as the ‘designated transmitter’ in a formation) continually transmitted then only one aircraft could be tracked on a given radio frequency, hence the contactor. This enabled a timed transmission of fourteen seconds to be made every minute, by staggering the transmissions up to four aircraft (or formations) could be tracked on one frequency, with a gap of one second between each transmission.”
PIPSQUEAK centred on a Master Contactor, incorporating a “spring-driven clock the escapement of which beats twice per second. Each vibration … closes an electrical contact, which in turn transmits an electrical impulse to the remote contactor.” The remote contactor contains a motor-driven rotor, rotating once per minute. “During 14 seconds of each minute, the rotor causes the closure of an electrical contact and consequent completion of…” the circuit which includes the operating coils of the frequency-shifting relays.” The remote contactor would be mounted in the cockpit and operated by the pilot.

TimG

Thanks to both. That's great information Tim, this piece was way outside my knowledge and collecting sphere.

Best

D