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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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23rd Mar 2022, 7:52 pm | #1 |
Diode
Join Date: Mar 2022
Location: New Romney, Kent, UK.
Posts: 2
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Admiralty pattern AP 13231A sound operated telephones.
Hello All,
This is my first post so forgive me if i get anything wrong. I have been given a number of Royal Navy sound operated telephones I think 5 so far, all Mk XV but showing differences in time of manufacture, some made with large amounts of brass, and others mostly steel, I guess this was wartime economy and simplification kicking in. I have two of the base units working after a good clean up and polishing of contacts. but I am issues with handsets, I don't have a complete set of operational microphone/speaker elements. opening one up it has a magnetic coil attached to a diaphragm i have these at both the earpiece and mouthpiece end is this normal ? the i have one coil that measures 75ohms the rest open circuit. in other telephones of this era i have had carbon granule microphones at the mouthpiece. I'm a little confused. has any one got any expertise in these? Many thanks |
23rd Mar 2022, 10:45 pm | #2 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,118
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Re: Admiralty pattern AP 13231A sound operated telephones.
Sound-powered telephones use magnetic microphones to generate the small currents which are picked up by (often identical) receiving units, so what you have found is common to sound-powered units.
A carbon granule transmitter is effectively a pressure-dependent resistor in which sound waves vary the resistance to a voltage supplied by a battery, so would not work in a sound-powered unit.
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Mending is better than Ending (cf Brave New World by Aldous Huxley) |
24th Mar 2022, 8:32 am | #3 |
Diode
Join Date: Mar 2022
Location: New Romney, Kent, UK.
Posts: 2
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Re: Admiralty pattern AP 13231A sound operated telephones.
Thanks Dave for the information, as i've said up to this point i have only worked on F-type telephones.
So with this in mind the open circuit coils means i need to find some replacements or learn how to re wind the coils. HAs anyone found a maintenance manual for this model of telephone? |
24th Mar 2022, 3:30 pm | #4 |
Hexode
Join Date: Aug 2010
Location: Malvern, Worcestershire, UK.
Posts: 340
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Re: Admiralty pattern AP 13231A sound operated telephones.
Played a bit with S.P. Kit when I was a kid, The elements are likely to be T.M.C if they are British made or a variety of U.S makes if lease lend, US makes are typically RCA and Western Electric along with Stromburg Carlson.
The DC resistance that you measure is correct. Do not be tempted to check operation with a battery as being balanced armature it is possible to cause a situation known as "pole over" and subsequent repair is very difficult. Once you have 2 elements with continuity they can be checked by interconnecting with 2 core cable and with each in a different room speech will be relayed from one to the other. I did come across some deck / gunnery head worn SP sets by TMC when going through some boxes last year and _IF_ yours are British T.M.C could be persuaded to have a look when a couple of recently broken ribs mend sufficiently. Mike Last edited by VT FUSE; 24th Mar 2022 at 3:36 pm. Reason: Additional info |
24th Mar 2022, 6:49 pm | #5 |
Heptode
Join Date: Apr 2010
Location: West Midlands, UK.
Posts: 659
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Re: Admiralty pattern AP 13231A sound operated telephones.
I bought a pair of these recently, the boxes with them have a switch and buzzer powered from what looks to have been a 1.5v battery and look home made. The switch has an RAF code, the buzzer is an ESL type also used by the RAF.
The handsets are type TMC AP.13220 and worked when connected together, low volume but clear. Does anyone recognise what the boxes were intended for originally? Mike. |