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Old 19th Sep 2017, 5:15 am   #19
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,188
Default Re: REN, Resistors &c.

I drew out the circuit of one of those REN boosters some time ago. If anyone wants a copy of it, get in touch. It's quite simple, using a quad darlington optoisolator, a small relay, a 45-0-45V mains transformer and a handful of small components.

Normally all wires of the output side are connected to the corresponding pins of the input BT Plug 431A, so that anti-tinkle works correctly. When it detects a ring signal, the relay operates, disconnecting the output side bell shunt wire from the input side and connecting it instead to a couple of sections of the optoisolator. These are driven by the incoming bell signal and switch the output bell signal between +65V and -65V at the incoming ringing frequency (+/-65V obtained by rectifying the output of the transformer, of course).
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