Path: utzoo!attcan!uunet!snorkelwacker!usc!cs.utexas.edu!asuvax!ncar!umigw!mthvax!wb8foz
From: wb8foz@mthvax.cs.miami.edu (David Lesher)
Newsgroups: sci.electronics
Subject: Re: Ring signal generation (was DTMF Decoder IC)
Message-ID: <1990Oct9.221432.6809@mthvax.cs.miami.edu>
Date: 9 Oct 90 22:14:32 GMT
References: <14793@mentor.cc.purdue.edu> <27114b84-483.1sci.electronics-1@vpnet.chi.il.us> <14913@mentor.cc.purdue.edu> <9770@uhccux.uhcc.Hawaii.Edu>
Reply-To: wb8foz@mthvax.cs.miami.edu (David Lesher)
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Organization: NRK Clinic for habitual NetNews Abusers
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I'm not clear if the original poster wanted to trip the ring
detect in his key system, or generate ring signal to run the
phones themselves.

In the first case, 60 hz will trip a 1A2 KTU 400 card with no
problem. I do recommend an isolation transformer -- about 70
volts RMS should do the job.

BUT, 60hz will not run any mechanical ringer I have seen. The
normal untuned ones will function on 30hz, however, and most of
the simpler KTU supplies actually make that.

You have several choices:
	Try phones with tweedle-deedle ringers. Note that some
	of those ringer chips are designed with 60hz rejection
	to avoid false ringing....

	Use DC buzzers in the phones, and forget the ringers.

	Make some 20/30 hz.

You may be able to find a supply with this feature at a hamfest.  The
WECO 113A, 117A&B, and the 20 and 30 series supplies all have ringer
voltage supplies. Lorain Products Corp. made thousands of "Sub-Cycle"
supplies of various styles and sizes.

Making your own supply is not impossible, but is likely
non-cost_effective. Exotic magnetics are needed to copy LPC's methods.
You could likely build a 30hz oscillator, and follow it with power
amps, but again that would be $$$.

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