691
The 691 set, or outfit CUH is a UHF transmitter and receiver set, built for the Admiralty during the fifties.
Below: Transmitter
Below: Receiver
COMMENTARY
The 691 set is a VHF transmitter and receiver set, capable of transmitting AM, CW, MCW or FM.
Channel is selected from one of ten crystal controlled channels.
TECHNICAL SPECIFICATIONS
Frequency Range: 277-283MHz ten channel crystal controlled
Modes: AM, FM, MCW, CW
Power Output: 10 Watts
CONSTRUCTION
The 691 receiver and transmitter are mounted in two separate cases. Each unit has a power supply drawer, and a transmitter or receiver drawer. Layout is classical Admiralty style, with monstrous power components mounted together in the bottom of the unit in their own tray, and the electronics mounted in its own tray.
Below: Transmitter Power Supply drawer. 
Below: Transmitter drawer. The ten channel crystal oven is at bottom right of
picture. The final tube is at top centre of picture.
Below: Receiver power supply drawer.
Below: Receiver drawer