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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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File Type: pdf REN_booster.pdf (458.7 KB, 35 views)
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