| Wireless for the Warrior - Volume 2 |
Supplement No. 5 |
Wireless Set No. 19
Note: The below described No. 19 Set improvised remote control and external tank telephone were two completely different arrangements.
The remote control was merely an extension of one of the crew Microphone and Receiver Headgear Assemblies allowing control of either A set, B set or intercom
via a two wire line when the tank or other type of vehicle was at the halt.
The external telephone, however, was fitted in a protective box at the rear of the tank and had intercom facility only.
The physical shape of the handset of both systems was similar, though components and circuit differed.
Improvised remote control.
In the early and mid World War 2 period considerable attention was paid in various theatres of war to the provision
of a light and compact remote control system for the Wireless Set No. 19, particularly for AFV and Royal Artillery requirements.
One local solution, for some time standard in the Middle East was the 'Bean' system.
This improvised remote control was locally constructed and made up from standard War Department Ordnance spare parts. The 'local' unit housed in a
small box, for example a spare Junction Distribution No. 1 or 2, and was normally fitted in the tank turret near the Commander's control box..
The absolute minimum of operation was required at the 'remote end', this consisted of a handset only,
connected to the improvised remote control junction box via normal available two wire Q22 or field cable on Reel Cable No. 1 mounted at the rear of the tank turret.
The handset was made up from a standard Microphone and Headgear Assembly No. 1 with one earpiece mounted on the microphone.
The original moving coil Microphone No. 7 was exchanged for a carbon type Microphone No. 3.
General layout of improvised remote control system. The handset is connected via a two wire line to the remote control junction box.
This box is connected to the standard No. 19 Set Control Harness.
Circuit diagram of locally constructed remote control junction box.
The five wires on the left hand side of the circuit are connected to the terminal strip inside the Commander/Gunner control box in the tank.
This allow switching to A set, B set or intercom.
The transmit/receive relay L (activating contacts LS1 to LS3) is a spare No. 19 Set transmit relay.
The transformer T is the microphone transformer T7A normally found in Junction Distribution No.1 or No.2 and is used as a set to line transformer.
One half of the low impedance winding carried audio from the set, the other half carries microphone audio. The higher impedance winding of the transformer,
which is connected to the two wire line, is used alternatively as audio secondary or microphone primary.
Circuit diagram of modified Microphone and Headgear Assembly No. 1. Only one earpiece is used (with a condenser in series for blocking the DC)
and the microphone is a carbon type.
In the corresponding Snatch Socket the microphone is connected in parallel with the earpiece and the two wires terminated to the reel cable.
The Blue wire marked ** is not used.
This is previously the transmit/receive contact, but now taken over by the microphone current actuating the relay in the remote control junction box.
Much later in the war Junction Remote Control No. 1 and No. 2 were issued for this purpose, partly based on the 'Bean' system, but not so compact.
See pages 22 and 23 of the 'WS 19 Control' paragraph in Wireless for the Warrior Volume 2
External telephone on Sherman tank intercom system for Infantry use
To allow the Infantry communicating in the No. 19 Set tank intercom system an external telephone handset was
connected to an additional standard driver's type Junction Distribution No. 3.
This assembly was mounted outside of the tank in a protective container bolted at the rear of the tank about midway between the exhaust stacks.
It was wired into the No. 19 Set intercom system via a protective cable
run through the tank hull to the terminal strip in the normal Junction Distribution No.3 (the driver's box).
To allow the Infantry user of the external tank telephone some freedom of movement for observation, the drop lead on the external
Junction Distribution No. 3 was 30 ft in length.
The improvised telephone handset for Infantry communication was ingeniously made up from a standard No. 19 or No. 22 Set type
Microphone and Headgear Assembly No. 1 or driver's type No. 2.
It is interesting to note that it is physically nearly impossible to use the handset in the normal way and whilst speaking the earpiece cannot be used.
Mechanical arrangements of fitting a single earpiece to the dynamic type Microphone Hand No. 7, part of Microphone and Headgear Assembly No. 1.
(Click to enlarge)
Alternative arrangements of fitting a single earpiece to a carbon granule (Tannoy) type Microphone Hand Power No. 1A,
part of Microphone and Headgear Assembly No. 2. The microphone is slightly modified, by two machined flat surfaces on the handle,
to which is bolted the bracket for the microphone, part of the standard headset headband.
The VAOS number YA 28968 is handwritten on the end of the microphone.
(Click to enlarge) Pictures courtesy Chris Clotworthy GI7TEU
END
Wireless for the Warrior
