AIR DEFENCE TELEPHONES

The GPO made many of the Observer Corps telephones and other equipment for the RAF.  These would always prefixed with the letters 'AD' for Air Defence, followed by a number .  This was in fact the GPO diagram number.  Most of the Air Defence apparatus was produced in the GPO Factories at Holloway, in London, and Birmingham.  Because of this they will also be marked with 'FH' or 'FB'.

TELEPHONE, PORTABLE AD 163
TELEPHONE, OBSERVER, DC SIGNALLING AD 599
TELEPHONE, OBSERVER AD 1542

CONTROL TOWER DESK MICROPHONE - Candlestick, normally marked 10A