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Old 06-08-21, 13:42
Chris Suslowicz Chris Suslowicz is offline
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Join Date: May 2007
Location: England
Posts: 765

Originally Posted by Mike Kelly View Post
I am wondering if the Aust. M.G. Carrier setup has the driver using a Tannoy style carbon insert Mic. or the normal No. 7 moving coil Mic ?

I hope the Aust. Carrier setup has the Tannoy style Mic. because I have one !
Sadly, no. The Headset & Microphone assembly No.2 with the Tannoy microphone is specifically for use in AFVs (mainly early tanks) for intercom (only) using Junction Distribution No.1 or No.2. This was necessary as there were not enough slip-rings in the rotary base junction (providing connections for turret wiring) to allow the standard intercom to be used. (The WS19 was mounted in the turret bustle and they could only scrape up two connections to the tank hull.) The intercom got 12V and ground from the hull wiring and the two circuits through the rotary base were Speech (output of the intercom amplifier) and Signal (input to the commander's headset for the buzzer call operated by the button on JD1 (JD2 did not have the call button or buzzer)).

The Tannoy microphone contains a double-button carbon insert which drove a centre-tapped transformer, the output side of which connected to ground and Speech. The Speech & Signal lines went into the rotary base junction, from there they appeared in the WS19 power junction box, and a fully-wired 6-way cable (+12 heaters, +12 Dynamotor, -12 Heaters, -12 Dynamotor, Speech, Signal) connected to the supply unit. Speech, Signal and the +12 Heaters (along with HT1 and HT2 and Ground) were passed through the dogbone connector into the set, and Speech + Signal went straight through to the 12-way harness connector for the control units (along with a 12V feed for the "A set unattended" warning light.

The 6-way dogbone was also fully populated, so when they needed relay control (for twin dynamotor or the Canadian vibrator+dynamotor supply units) they had to fit a 12-way connector for power input to the set, or bodge the existing 6-pin one (lifting the ground connection on Pin 1 and using that for the relay line and the braided screen for the ground connection) and using a 12pin - 6pin dogbone to feed the modified set.

Best regards,
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