Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!boulder!sunybcs!oswego!penelope.oswego.edu!vermilye
From: vermilye@penelope.oswego.edu (Jon R. Vermilye)
Newsgroups: sci.electronics
Subject: Re: Ringing telephones with line voltage
Keywords: bandpass filters: are they there?
Message-ID: <1229@oswego.Oswego.EDU>
Date: 10 May 89 20:53:30 GMT
References: <636@serene.UUCP> <920@snjsn1.SJ.ATE.SLB.COM> <3139@kitty.UUCP> <5012@charon.unm.edu> <3144@kitty.UUCP>
Sender: news@oswego.Oswego.EDU
Reply-To: vermilye@penelope.oswego.edu (Jon R. Vermilye)
Organization: SUNY, Collego at Oswego
Lines: 48

In article <3144@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes:
>In article <5012@charon.unm.edu>, ee5391aa@hydra.unm.edu (Duke McMullan n5gax) writes:
>> >	Sorry, but you canNOT ring a phone with "house current".  Virtually
>> >all conventional telephone ringers are frequency selective, and operate only

>> Wellll -- I do it on occasion. I generally pull the voltage down to about
>> 90 VAC with a variable autotransformer for safety, but the 'phone rings loudly
>> and continuously.
>
>	Well, I suppose anything is possible if you drive the ringer hard
>enough.  

>	Under the circumstances, I bet you were either: (1) driving the
>ringer at current levels >> greater than 50 mA, and/or (2) driving the
>ringer without the usual series capacitor.
> 
>> If you close the hookswitch, you get a loud buzz. ;^)
>
>	See any smoke? :-)

	I have to add my 2 cents.  We have been ringing phones with 60
Hz AC for years.  I just finished measuring the ringing current on a 
standard C/D 500 (old black non-electronic) phone - 40ma.  Of course
the ring is not normal, but it does ring, and the current is reasonable.

	The best solution for ringing phones for the theatre is to get
a ringing generator.  We use a Tellabs 8101, which produces 90 - 120 v
AC at 30Hz.  The phone will sound normal and the ferro-resonant saturable
core reactor limits the output to about 5 watts.  It cost about $60.00
in 1980, and since it is is a mechanical, ie transformer, device, it puts
up with the abuse that theatrical technicians can provide.  By the way, 
if you plan to answer, ie pick up the reciever of the phone, be sure to
remove the earpiece.  You don't have the CO to shut off the ringing 
voltage, and 30 or 60 hz at ringing current will annoy the actors ;^).

	I also suggest that you modify the phone so that lifting the 
handset will open the ringing circuit.  You can use some of the 
normally closed contacts on the hanger switch.  This will prevent the
situation where the phone is ringing while the actor holds it in 
his hand.  I suspect that many of these modifications swould be more
difficult on an electronic phone, however is should still ring with 
the ringing generator.

 
Jon R. Vermilye                          		         315 341 2138
Department of Theatre                              vermilye@oswego.Oswego.EDU
SUNY Oswego                                   rutgers!sunybcs!oswego!vermilye
Oswego, NY 13126