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Old 10th Aug 2019, 9:20 pm   #1
dagskarlsen
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Default 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
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Old 23rd Aug 2019, 12:05 am   #2
Oldcodger
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Default 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 .
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Old 23rd Aug 2019, 7:21 am   #3
Dave Moll
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Default 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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Old 23rd Aug 2019, 4:07 pm   #4
dagskarlsen
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Default 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.

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Old 26th Aug 2019, 3:46 pm   #5
TonyDuell
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Default Re: Boost the ringer current instead of ...

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'.
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Old 6th Oct 2019, 1:41 pm   #6
dagskarlsen
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Default 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

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Old 6th Oct 2019, 3:50 pm   #7
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Default Re: Boost the ringer current instead of ...

Quote:
Originally Posted by Dave Moll View Post
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).
Dave - the one I referred to was fitted inside a full sized socket, with provision for a 50 supply from a BT SWITCH . Only markings I can find on any of the few I have is DPA/1448/A . 5 TRANSISTORS but no sign of an opto coupler.
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 .
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Old 6th Oct 2019, 5:46 pm   #8
dagskarlsen
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Default Re: Boost the ringer current instead of ...

Quote:
Originally Posted by dagskarlsen View Post
I have been working further on my circuit to just keep 2 wires.

http://www.classicrotaryphones.com/f...h=211423;image

dsk
Just tested today, and yes it works, the excchange can not monitor the REN load.

Drawbacks:
1) polarity sensitive, does not accept reverse polarity.
2) The ring current continiues until the relay release.

dsk
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Old 8th Oct 2019, 8:10 am   #9
dagskarlsen
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Default 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

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