BOWMAN@DARTCMS1.BITNET (Phil Bowman) (11/24/87)
Does anyone out there know how to put a switch on a residential telco line (the red and green wire) to simulate a busy condition to incoming callers and to suppress the ring of the phone itself? Is there a way to add a neon light to show the line is off-hook (I think there are 90 volts on the line)?
dp@JASPER.PALLADIAN.COM (Jeffrey Del Papa) (12/04/87)
Date: Tue, 24 Nov 87 09:02:34 EST
From: Phil Bowman <BOWMAN%DARTCMS1.BITNET@MITVMA.MIT.EDU>
Does anyone out there know how to put a switch on a residential telco line
(the red and green wire) to simulate a busy condition to incoming callers
and to suppress the ring of the phone itself? Is there a way to add a
neon light to show the line is off-hook (I think there are 90 volts on the
line)?
ring prevention is fairly easy - a pair of diacs in series across the pair will
block ringing (a diac is a bistable 4 layer diode, below the threshold (40 volts
typically) it is an open circut, above it, a short.)
All subscriber loops have protective devices on them that shut down a voltage
source if a short is detected. thus ring (90v) is put on the loop, the diacs
conduct on the first half cycle, and the ring is removed from the loop. this
doesn't count as call completion, so the other party will often hear ringing
continue. diacs used to be available at rat shack, they may still be.
<dp>roy%phri@UUNET.UU.NET (Roy Smith) (12/04/87)
Connecting a garden variety resistor in the 600-1000 ohm range
between tip and ring (i.e. red and green, unless your line is wired funny)
will give an off-hook condition. You probably want a fairly hefty (2 Watt)
one just to be safe. Connecting a normal household 25 Watt light bulb
across the line will get you light when the phone rings (although the phone
company may not appreciate this; I have no idea what the ringer equivelance
number of a light bulb is :-)).
--
Roy Smith, {allegra,cmcl2,philabs}!phri!roy
System Administrator, Public Health Research Institute
455 First Avenue, New York, NY 10016jbh@mibte.UUCP (James Harvey) (12/22/87)
In article <871203231158.1.DP@BANFF.PALLADIAN.COM>, dp@JASPER.PALLADIAN.COM (Jeffrey Del Papa) writes: > > Date: Tue, 24 Nov 87 09:02:34 EST > From: Phil Bowman <BOWMAN%DARTCMS1.BITNET@MITVMA.MIT.EDU> > > > Does anyone out there know how to put a switch on a residential telco line > (the red and green wire) to simulate a busy condition to incoming callers > and to suppress the ring of the phone itself? Is there a way to add a > neon light to show the line is off-hook (I think there are 90 volts on the > line)? > > > ring prevention is fairly easy - a pair of diacs in series across the pair will > block ringing (a diac is a bistable 4 layer diode, below the threshold (40 volts > typically) it is an open circut, above it, a short.) > All subscriber loops have protective devices on them that shut down a voltage > source if a short is detected. thus ring (90v) is put on the loop, the diacs > conduct on the first half cycle, and the ring is removed from the loop. this > doesn't count as call completion, so the other party will often hear ringing > continue. diacs used to be available at rat shack, they may still be. > > <dp> Radio Schlock used to sell (think they still do) a device to suppress the ring. I think it's under ten bucks. It is popular with owners of the Commodore 1670 Modem which defaults to auto-answer every time you reset the computer. A resistor will busy out the phone but after a while the switching machine thinks there is trouble on the line and will disconnect it. It may be a while before you can get dial tone again after you remove the resistor. You might try simply ringing up some local recording and laying the receiver down on the table. -- Jim Harvey | "Ask not for whom the bell Michigan Bell Telephone | tolls and you will only pay 29777 Telegraph | Station-to-Station rates." Southfield, Mich. 48034 | ihnp4!mibte!jbh or try ulysses!gamma!mibte!jbh