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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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29th Sep 2012, 12:27 pm | #1 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,118
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Can anyone help identify this telephone?
Among a job lot of 700-series telephones acquired recently was the instrument pictured below. Apart from the eight buttons and two LEDs, it is a perfectly normal 746-type telephone.
It is presumably for use within some sort of PABX setup - with the two front corner buttons for selection of two exchange lines, and the other six presumably for signalling other extensions. All buttons are non-latching. The interesting (to me at least) thing is the way the switches and LEDs are wired. The eight buttons are integral to a single sealed switch block with a single pair of wires emerging from it. Also, the LEDs are connected in parallel to a second single pair of wires. I assume, therfore, that the LEDs are wired in opposite polarity so that the polarity of the incoming signal determines which one lights up. The switch block presumably sends a coded signal according to which button was pressed. My first question is whether anyone knows what system would use this as an extension, as the system would have to be designed to accept and send the appropriate signalling. Incidentally, the 'phone uses a six-way line cable wired as follows: white: A leg red: B leg green: bell* blue: common between switch block and LEDs black: switch block orange: LEDs *As the internal ringer capacitor is used, this would provide a ringing signal to a parallel external ringer. As all but the red and white wires had had been snipped off at the external end of the line cord, I have now replaced the it with a six-way plugged lead I happened to have (originally intended for another project) and converted the 'phone to use the blue wire for ringing signal from an external master socket ringing capacitor, so that blue and green have now swapped functions and the internal capacitor is no longer used.
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29th Sep 2012, 4:53 pm | #2 |
Octode
Join Date: Aug 2005
Location: Saltburn-East, Cleveland, UK.
Posts: 1,786
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Re: Can anyone help identify this telephone?
Hi,
It's possibly from some multi line plan system, the legends between the switch hooks will be the indications of which switch does what when in the operated or released position. You mention that non of the buttons latch, but is there any indication that a latch plate has even been fitted (or still present) as you don't know if this has been tampered with at any time. It might have been from a modified plan 2A, alternatively it could have been intended for Data (with an external modem) or Telex use; remember that, at one point in time, the GPO/BT insisted that you must be alerted to all incoming calls, which led to things such as telex machines and modems, Viewdata terminals etc. always being provided with an accompanying telephone. I have just noticed that it carries the legend FMC on the base which might suggest Ferranti manufacture. Regards Andrew Last edited by AndiiT; 29th Sep 2012 at 4:54 pm. Reason: Changed information |
29th Sep 2012, 7:02 pm | #3 |
Heptode
Join Date: Apr 2011
Location: Edinburgh, UK.
Posts: 805
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Re: Can anyone help identify this telephone?
The bell volume slider and the bell grilles are non-GPO. I'll guess that it's a Railway version of a HES 3
http://www.britishtelephones.com/hes3.htm |
29th Sep 2012, 9:22 pm | #4 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,118
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Re: Can anyone help identify this telephone?
Having looked at the wiring diagrams for the HES3, that seems to use multi-way cabling between extensions, whereas (as I said above) the only additional connections over and above those for a standard telephone are one pair for the switch block and one pair for the LEDs.
Incidentally, it does surprise me that an instrument as early as a 746 type telephone uses LEDs, but close inspection does seem to confirm that they are typical bowler-hat-shaped red LEDs.
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29th Nov 2012, 1:03 pm | #5 |
Heptode
Join Date: Jul 2007
Location: Flintshire, UK.
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Re: Can anyone help identify this telephone?
It is the later 746 version of the 'Multiphone' system http://www.britishtelephones.com/ericsson/multiph1.htm sold by Plessey or used on PAX systems.
The 74X phones did have LED units which fitted into the case either side just above the dial. I have a 746CB with such LEDs. But the telephone in the photo appears to have the opals for use with 'Lamp Fitting No 16A or 17A' for PO phones. Last edited by Dave Moll; 29th Nov 2012 at 5:17 pm. Reason: link corrected |
29th Nov 2012, 5:36 pm | #6 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
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Re: Can anyone help identify this telephone?
Many thanks for that link. That certainly looks like the right system. Although the pictured telephone doesn't have the second exchange light, it looks otherwise pretty much the same.
Mind you, I probably stand I higher chance of being hit by a flying pig than I do of acquiring the appropriate control unit.
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29th Nov 2012, 5:43 pm | #7 |
Octode
Join Date: Aug 2005
Location: Saltburn-East, Cleveland, UK.
Posts: 1,786
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Re: Can anyone help identify this telephone?
Hi, I have sent you a PM about this phone.
Andrew |