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From: lairdkb@mentor.cc.purdue.edu (Kyler Laird)
Newsgroups: sci.electronics
Subject: (Telephone) Ring Generator
Message-ID: <1902@mentor.cc.purdue.edu>
Date: 28 Nov 90 16:07:12 GMT
Reply-To: lairdkb@mentor.cc.purdue.edu (Kyler Laird)
Distribution: usa
Organization: Purdue University
Lines: 22

I had many requests for my ring generator schematic.

Recently I saw a project similar to the one I built for EE in Modern Electronics.

I'll outline our approach.

get 12VDC
switch it with an optoisolator 
connect output to secondary of a 120V-12V transformer
connect primary of xfrmr to telephone

pulse the optoisolator with a 555 at 20Hz

use another 555 (or just a 556) to interupt the ring signal (rrring...rrring...)


Like a dummy, I didn't use the transformer.  Instead, I played around with a
push-pull approach using about 48VDC per side.  Didn't have the power I needed
to ring mechanical ringers.  I have hopes that the higher voltage will do it.
I doubt the current I was providing did any good.

--kyler