Path: utzoo!attcan!uunet!munnari.oz.au!uhccux!hale!whinery
From: whinery@hale.ifa.hawaii.edu (Alan Whinery)
Newsgroups: sci.electronics
Subject: Re: Ring signal generation (was DTMF Decoder IC)
Message-ID: <9770@uhccux.uhcc.Hawaii.Edu>
Date: 9 Oct 90 19:42:13 GMT
References: <14793@mentor.cc.purdue.edu> <27114b84-483.1sci.electronics-1@vpnet.chi.il.us> <14913@mentor.cc.purdue.edu>
Sender: news@uhccux.uhcc.Hawaii.Edu
Organization: Institute For Astronomy, Hawaii
Lines: 22

In article <14913@mentor.cc.purdue.edu> lairdkb@mentor.cc.purdue.edu (Kyler Laird) writes:

>2) Any ideas on _creating_ a ring signal?  I'm trying to route an incoming
>call to a device.  I've found out that a 'standard' ring is 48vdc @ 20Hz. 
>--kyler
ccording to "Understanding Telephone Electronics" which I bought at Radio
Shack in Tippecanoe Mall some years back, the correct ringing signal on 
a spec FCC telephone set (ha ha ha, find one) is 90 VRMS @ 20 hz. I think the 
48 volts you mentioned is probably the "battery" DC line voltage that appears
when the line is at high impedance (off-hook). The ring signal in 
West Lafayette is a pulsed one, meaning that it contains little bursts of
the 20 hz during a ring, rather than a constant 20 hz. 

To emulate this? Your ringer would probably eat 60 hz, but you'd have to 
knock down the voltage a little, and it would sound funny. The likelihood
that there is a high Q 20 hz filter in a phone is relatively slim. 
It would be cool if you had an autotransformer, with which you could vary
the AC voltage from a line socket to experiment. 

Alan Whinery
whinery@hale.ifa.hawaii.edu
BSET Purdue 1984