Boost the ringer current instead of ...
I made a system for making more ring power, and that will also fit the UK-system. The relay will almost draw nothing from the line, and the output to the third wire will not be affect the incoming ring power.
For UK I would suggest to add e 1.8 uF capacitor in series with the ring line, just because of the characteristics of the AC inverter. http://www.classicrotaryphones.com/f...9848#msg229848 dsk |
Re: Boost the ringer current instead of ...
dag- BT had two alternatives, designed for use with systems ,mainly to drive an external bell.
One was a master size wall face plate with a transistor ringer in it, powered from a 50v feed from a system. The other was a mains driven converter ringer. Possibly the blokes wh worked on BT systems in that era wil have more info . |
Re: Boost the ringer current instead of ...
In the days before I had my extensions hung off a PABX, I used a plug-in unit (with a REN of 1) which was presumably the converter referred to above. Its output supported of REN of up to 8, allowing a total of REN of 11 (inluding 3 connected direct to the incoming line).
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Re: Boost the ringer current instead of ...
I just bilt it in lack of other solutions. I use it on a mobil phone adapter together with a dialgizmo. That solves my need for using old phones on that system.
dsk |
Re: Boost the ringer current instead of ...
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I have (I hope) attached a reverse-engineered (by me) circuit diagram of the ringer booster that was commonly sold in the UK some years ago (maybe BT-badged).
Note that the opto-isolator is a rather odd one with a very high current transfer ratio (ratio of LED current to output current). It will not work with just 'any old optoisolator'. |
Re: Boost the ringer current instead of ...
I have been working further on my circuit to just keep 2 wires.
http://www.classicrotaryphones.com/f...h=211423;image dsk |
Re: Boost the ringer current instead of ...
1 Attachment(s)
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Photo attached. The connector is marked (LH, from Top) DCBA and the right hand one 9 from top) 47v , bell( pair) and 0v .No protective diode in the power line, so if volts reversed ,R6 TENDED TO GET HOT. Wired up correctly it had more than enough power to drive an extension bell Or there's the convertor ringing 2A ,ITEM CODE 375507, normally used with a key system to power an extension bell from extensions ( from memory) set to ring on an incoming call . |
Re: Boost the ringer current instead of ...
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Drawbacks: 1) polarity sensitive, does not accept reverse polarity. 2) The ring current continiues until the relay release. dsk |
Re: Boost the ringer current instead of ...
Now, I have been testing it out, and it had to be modified. It was to sensitive and could make trouble when dialing out, so I did put in another zener diode back to back wit the first one, and that solved the problem.
Mdified wiring diagram is here: http://www.classicrotaryphones.com/f...1742#msg231742 dsk |
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