TYPE 685 P
Frequency Range Transmitting Set Receiver Outfit
85-95Mc/s Type 685 Transmitter 7AL AP W7943A CDK [Receiver P40] AP W7945A
65-75Mc/s Type 685 Transmitter 7AL  AP W7943A and Conversion Kit AP 58250 CDQ [Receiver P40] AP 56187A

It is used on vehicles and other craft as the main or supplementary equipment. It may be installed with or without remote control and may be set up for SIMPLEX or DUPLEX working.

It is crystal controlled and operates [TX and RX] on pre-determined spot frequencies.

There are 3 separate chassis for the power supplies plus an additional power supply mounted on the speech amplifier chassis which give the LT and the speech amplifier supplies.

Power output was 100 Watts.

A station set up to use Type 685 and outfit CDK or Type 685 + Conversion Kit and outfit CDQ, requires, in addition, one or more of the aerial outfits AGU, AGY, AGW, AGP or AGO, which are supplied separately, and one or more of the following outfits:-

  • Control Outfit KSC - for simplex working only.
  • Control Outfit KSD - for duplex working with NO LINKING outfit employed.
  • Control Outfit KSF - for duplex working WITH a LINKING unit employed - this outfit is required where the AUDIO input and output are to be extended for other purposes e.g. connection with a field telephone exchange or relaying through another circuit.
  • Aerial Switching Unit Outfit ESC - for simplex working only.

In its time [1946] this set can either be thought of as 'simple' or 'very sophisticated', the latter having every conceivable device option fitted to the Type 685. The FACILITIES available were as follows:-

Simplex Available with either local or remote positions.  In both instances HT switching of the transmitter is carried out by means of the pressel  switch in the handset.
Duplex Operation is available with either local or remote positions. HT switching of the transmitter is or is not possible at the handset according to the outfit used. With duplex operation, the radio station can be connected to a field telephone exchange so that any extension of this exchange can speak over the radio link.
Teleprinter Teleprinter operations of a duplex link is possible. This requires a teleprinter, teleprinter terminal unit, teleprinter rectifier unit and an S + DX MkII in addition to the outfits described.
Relay Where 2 complete installations are fitted in close proximity to one another, as in Radio Van 19A, the installation may be linked together so that what one station  receives can be re-radiated on the other circuit and vice versa. 

Click on this file to see the full Duplex Linking System  685 DUPLEX LINKING.pdf
This to see the unit wiring and connections for the system 685 unit wiring.pdf


685 radio relay rack with cover lowered.