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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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29th Apr 2020, 1:54 pm | #1 |
Heptode
Join Date: Oct 2006
Location: Leeds, West Yorkshire, UK.
Posts: 597
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Bellset 48 and Tele 713
Latest project is to connect a Tele 713 to a Bellset. The 713 handset has a flashing neon (and a six core handset cord) and I plan to use this instead of the bells. No dial so I shall strap T8 and T10 together. Should I disconnect the bell altogether ? Will I still need to install a 3.3k resistor ? Are there any other wiring considerations I need to be aware of ?
So many questions! Thankyou. |
29th Apr 2020, 3:15 pm | #2 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,642
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Re: Bellset 48 and Tele 713
BT N diagram for the neon handset: http://www.samhallas.co.uk/repositor...1000/N1901.pdf
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29th Apr 2020, 3:18 pm | #3 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,129
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Re: Bellset 48 and Tele 713
If you are using a neon in place of bells, it will certainly need a series resistor to limit the current through the neon once it fires - probably a somewhat higher value than 3.3k.
Looking at a unit I built for interconnecting field telephones where I used neons for this purpose, I see that I selected a value of 22k. As I recall, I arrived at this value by starting high and reducing until I received a satisfactory glow from the neons without over-stressing them, but others may be able to supply a more scientific rationale for an appropriate value. edit: my reply is, I believe, superseded by Bill's link.
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Mending is better than Ending (cf Brave New World by Aldous Huxley) |
29th Apr 2020, 3:45 pm | #4 |
Heptode
Join Date: Oct 2006
Location: Leeds, West Yorkshire, UK.
Posts: 597
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Re: Bellset 48 and Tele 713
Thankyou both.
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29th Apr 2020, 10:00 pm | #5 |
Octode
Join Date: Aug 2005
Location: Saltburn-East, Cleveland, UK.
Posts: 1,786
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Re: Bellset 48 and Tele 713
Hi, originally the neon in the handset was connected across a resistor in series with the 1K bell coil, the value of the resistor differing depending on whether there was an additional extension bell fitted.
With a 4K bell you have to experiment with the resistor value and I found that with a 700 type phone wired for "plug and socket" working, the easiest way to get the neon to strike was not to connect the neon and its associated series resistor in parallel with the bell circuit but instead exploit the unused bell capacitor in the phone to provide current for the neon. I understand that you aren't using a 700 type phone however it may be possible to achieve lamp calling by the neon by connecting the neon in parallel with a 1k resistor (to emulate the bell) and then experiment with a value of series resistor to get the neon to strike brightly enough upon receipt of an incoming call. Regards Andrew |
30th Apr 2020, 8:15 am | #6 |
Heptode
Join Date: Oct 2006
Location: Leeds, West Yorkshire, UK.
Posts: 597
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Re: Bellset 48 and Tele 713
Thanks Andrew. Plenty to be thinking about there. The bellset I have has 1k bells do if I decide to leave them in, I expect I'll still need to add a 3.3k resistor.
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