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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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12th Nov 2008, 8:51 pm | #21 | |
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Re: Telephone set F
Quote:
Just a few feet of bell flex at the moment, although the XYL has promised to help me run a test over 30 metres later tonight, using 3 volt batteries as per the original specification. I only really need these telephones to work over a few hundred metres. I am, however, interested in how these instruments worked in the field with 3V batteries... were the signallers expected to bellow into them?! Thanks for all the advice,
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12th Nov 2008, 9:31 pm | #22 | |
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Re: Telephone set F
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I'll get back to you about the voltages later, but it's occurred to me that you should check the induction coils in your telephones. Any damage visible? Can you buzz out the pins on the ends of the ASTICs and check out continuity WRT the drawing? I think it unlikely that you will have shorted turns on them, particularly as your low-level sound is on both instruments, but it may be worth a look. Some ASTICs have their resistances written on a slip of paper, visible beneath the outer layer. Is the sound level different when the telephones are connected to when they're open-cct?
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12th Nov 2008, 9:40 pm | #23 | |
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Re: Telephone set F
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It also looks slightly more modern than others I've seen. Anyone know when the type 'F's were superseded?
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12th Nov 2008, 11:22 pm | #24 |
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Re: Telephone set F
Russell,
I've tried the phones on 3 volts over 30 metres or so of thin bell wire, and although the volume is relatively low, it is acceptable. The sound in the earpiece is roughly the same when o/c as when linked by the line. I haven't tested the induction coils but they look perfect. It has struck me that I am using non-identical telephones together, an F and a D. I imagined they would be compatible, but maybe there's a line impedance mismatch? Anyway, I've got another F Mk II on its way, so I'll try the matching pair at the weekend and report back! Thanks for your continuing help and interest.
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12th Nov 2008, 11:47 pm | #25 | |
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Re: Telephone set F
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I was miles out with my 12V across the mic before; don't know what I was thinking of! Here are the measurements made on three telephones at Chez Barnes:
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15th Nov 2008, 9:25 pm | #26 |
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Re: Telephone set F
Interesting development - my second type "F" telephone has arrived, a non-buzzer model marked 'Telephone set "F" Mk II TMC'. It has exactly the same earpiece as in the photo posted by dkleeman, and is much more sensitive than my first phone which is badged 'Telephone set "F" Mk II PL' and has a traditional earpiece. Perhaps TMC stands for 'Telephone Manufacturing Company' and PL may be short for 'Plessey'?
Anyway, back to battery voltages... the TMC phone gives good audio when the PL phone is working from just 3 volts, but I have had to put a 6-volt battery into the TMC phone in order to get roughly equal audio level in the PL phone's earpiece. It would therefore appear that development led to the more sensitive earpiece being introduced to improve the audio level, rather than increasing the battery voltage - probably because there was no space for more S or X cells! Anyway, thanks to one and all for the interesting information you have supplied, and I am now pleased to own a working pair of Telephone Sets "F".
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15th Nov 2008, 10:19 pm | #27 | |
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Re: Telephone set F
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I have one military 'J'-type field-telephone fitted with such a receiver, and two civilian type-'J's (they're brown, not green) with the traditional 'Receiver, Inset, No:11' type of earpiece. There is certainly a difference in sensitivity. I'm pleased you got satisfaction in the end. What do you propose using them for?
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Regds, Russell W. B. G4YLI. Last edited by russell_w_b; 15th Nov 2008 at 10:31 pm. |
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15th Nov 2008, 10:34 pm | #28 | |
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Re: Telephone set F
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To avoid licencing difficulties I use the LSDSRs, which are land-based Aldis lamps capable of several miles range, although we use them over a path of just a few hundred yards. Talk-back between the adult instructors at each end has previously been via amateur radio, meaning that the activity requires two licenced hams - sometimes that's difficult on a busy weekend, so the field telephones have been obtained to permit non-licenced instructors to run the activity! It also will give the youngsters experience on another type of communications device. Thanks for your help in getting the phones going!
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15th Nov 2008, 10:48 pm | #29 | |
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Re: Telephone set F
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Regarding your use: best of luck! I did more-or-less the same thing with the Cubs. I taught them a bit of morse, and I have two Aldis lamps which I used similarly. We used short-range PMR446 walkie-talkies, though.
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15th Nov 2008, 10:52 pm | #30 |
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Re: Telephone set F
I'm glad to see them being put to a real use.
Perhaps your next acquisition should be a pair of telephone sets "D", complete with morse keys, to give yet another communications experience - but that would be a topic for another discussion. I can't imagine the buzzer button on an "F" (even if both are equipped with buzzer-type inductors) being particularly useable for morse sending.
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16th Nov 2008, 12:34 am | #31 | |
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Re: Telephone set F
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Well, I've got one type "D" already, so that's a good idea, and if anyone knows of another "D" going cheap, please give me a shout!
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