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From: zygot!john@apple.com (John Higdon)
Newsgroups: comp.dcom.telecom
Subject: Re: While Phone Rings, Charges May Begin
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Date: 10 Aug 89 17:41:26 GMT
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In article , tanner@ki4pv.uucp
(Dr. T. Andrews) writes:
> ) ... green box ... tone to payphone
> Do payphones not use out-of-band signalling?  It would seem to invite
> abuse if they used in-band signalling, especially if someone were
> inclined to carry a recording of money being dropped into the thing.

The insertion of money causes in-band signaling. It makes a little beep
that is muted so that you don't hear it. One beep per five cents. This
totals up on a display that the operator has in front of her (or on the
automatic coin collection equipment.) It is a trivial matter to imitate
these beeps with a device called a "red box". However, the first coin
must be real, since the phone signals via DC loop that there is indeed
at least one coin in the hopper (the first coin trips a flapper in the
chute which is reset each time the hopper dumps to either the coin box
or the return). If this signal is not present, they know you are
pulling something.

Pac*Bell has a few fraud prevention techniques to prevent this. One of
them is to periodically and without warning dump the hopper into the
coin box so that a new real coin will have to be inserted. Any
dicrepancies and you better watch out. There are others which I'll keep
to myself for now.
--
        John Higdon         |   P. O. Box 7648   |   +1 408 723 1395
      john@zygot.uucp       | San Jose, CA 95150 |       M o o !