TYPE 81 P


TYPE 81 TRANSMITTER

DATE OF DESIGN 1921
FREQUENCY RANGE 750 - 1500 kc/s
POWER SUPPLY Ship's DC Main either 220V or 100V.  The set has a nominal range of 2 miles is using 220V but this is considerably reduced with a 100V system.
TYPE OF SET VALVE
WAVEFORM RT and ICW
METHOD OF PRODUCING OSCILLATIONS SELF
WHERE USED/FITTED Type 81 is a low power valve set which was originally designed as an R/T transmitter but is now modified and has a separate attachment fitted for transmitting ICW.  The set can be operated from either of three fixed positions, usually W/T office, bridge/chartroom areas and Auxiliary W/T office.  The switch allowing this is marked "operator" and "control".  When set to "operator" the local [main W/T Office] Morse key/microphone is operable and when set to "control" both remote positions and the W/T office operator can operate the set. Further, each position has a 'local' and 'remote' switch.  When in 'remote' the operator at that position can key the transmitter and the other two operators can listen in to what is being said or tapped out on the Morse key.  All three operators can converse [passing procedural information or engineering/operating instructions] without transmitting live, by each switching to their 'local' position and to 'R/T'. In this case the power is provided by a 4.5V dry battery.
ASSOCIATED WAVEMETER 1492B or G9
SMALL SCHEMATIC

Look here to see the full system diagram whose numbers correspond to those shown below in the photograph 81 overall circuit.pdf

PHOTOGRAPHS

See above, to the full system circuit to understand the number shown.