Telephone Sets "F" High Power No.1 MkII

[Chris Suslowicz]

Originally Posted by David Dunlop

I have a pair of these telephone sets, that I assumed were also a Northern Electric WW2 production item (based on the sole fact they had been used by the Canadian Army and were surplused out here in Canada, and who else manufactured telephones here on a large scale. Finally had a closer look at them this morning and they are definitely not NE production. The only possible ID I found on either set was the letters 'T.M.C" cast into the bakelite on the bottom of each phone unit. No date of manufacture anywhere and the newer of the two sets shows a Broad Arrow stamp on the front of the phone, below the magneto crank. No ID info at all on the amplifier units of either set. So now I am wondering who made these telephone sets.

The older of the two sets is Serial # 362 and this one has a metal ID plate mounted on the top of the case. This plate has the name of the Telephone Set at the top and below it is probably a NATO Stock Number: 5805-21-106-5649

If that is a NATO Stock Number, then these sets were in service for quite some time.

The newer set, Serial # 1815 is the one with the Broad Arrow stamp on it. These sets do not appear to have any internal battery compartments which leads me to believe an external battery pack of some sort must have been used to operate them. Based on the amplifier schematics in the cases, these external batteries must have had a dual output capability of approximately 60 volts DC as the mains and somewhere between 1.5 and 6 volts for the valve filaments.

Not sure at what level (HQ or lower?) these telephones would have been used. The newer set does have a large yellow 'B" stencilled on one side of the case, but that does not tell me much.

David

The Telephone Set F was always an "office" telephone, used mainly at headquarters in conjunction with the Switchboard F&F[1]. The "High Power" version was for use where long lines (with considerable attenuation of the signal) were a problem.

There was a separate battery box that went with the unit (I have never seen one in the wood), that held 2 x 60 volt primary batteries and 3 x 2 volt lead-acid cells. The battery box weighed 27 pounds when complete!

The valve used in the amplifier is a CV65 or PEN25, a 2-volt directly heated pentode. and has a resistor in series with the filament. (The 6 volt LT supply is necessary for the send/receive relay coil.)

The amplifier provides 20dB gain on sending and up to 40dB on receive (to cope with noisy environments).

I suspect it was replaced by the "Amplifier, Field Telephone, No.1" which was fully sealed and powered by the WS18 type 162V/3V battery (and a fraction of the weight) in later years - that could be used with any standard field telephone.

The NATO Stock Number will be an "after the fact" issue, and does not reflect the actual country of origin[2] (the manufacturer was TMC (the Telephone Manufacturing Company of London, England)[3]).

Chris.
[1] Please do not restart the discussion over whether F&F stands for Field & Fortress or Field & Fixed. Both terms appear in documentation, but the actual manual for the beast doesn't expand the abbreviation!
[2] I have a WS19 'B' set aerial lead (No.3) ex-Italian surplus with an Italian NSN on the label, but a Pye metal tag with the original ZA stores code.
[3] http://www.telephonecollecting.org/B...es/TMC/TMC.htm