Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!apple!oliveb!pyramid!lll-winken!uunet!snjsn1!bilbo!greg
From: greg@bilbo (Greg Wageman)
Newsgroups: sci.electronics
Subject: Re: Using "Free" telephone power
Message-ID: <931@snjsn1.SJ.ATE.SLB.COM>
Date: 3 May 89 22:23:09 GMT
References: <636@serene.UUCP> <920@snjsn1.SJ.ATE.SLB.COM> <3139@kitty.UUCP>
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Reply-To: greg@sj.ate.slb.com (Greg Wageman)
Organization: Schlumberger ATE, San Jose, CA
Lines: 31

In article <3139@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes:
>
>> Even if you could, you would have to
>> cope with the possibility of an incoming ring signal, which is
>> typically 60-90 VAC!  (Yes, Virginia, you can ring a phone with house
>> current.)
>
>	Sorry, but you canNOT ring a phone with "house current".  Virtually
>all conventional telephone ringers are frequency selective, and operate only
>between 16 and 32 Hz; 60 Hz won't cut it.  Some ringers used on older
>party line systems (like the "harmonic", "decimonic" and "synchronic") were
>_very_ freqeuncy selective, with a "bandpass" of 5 Hz or less.

You are correct that the ring signal's frequency is nominally 20 Hz,
but you can ring a telephone with house current.  I have done it with
several different (Bell) telephones of varying vintage.  It isn't very
efficient, since the coils are tuned for 20 Hz, but it works.  (Of
course the set must be on-hook for this to work.)


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