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From: LENOIL@DEEP-THOUGHT.MIT.EDU (Robert Lenoil)
Newsgroups: mod.telecom
Subject: Re: Toll Restrictor
Message-ID: <8609010134.AA08345@ucbvax.Berkeley.EDU>
Date: Thu, 28-Aug-86 13:34:21 EDT
Article-I.D.: ucbvax.8609010134.AA08345
Posted: Thu Aug 28 13:34:21 1986
Date-Received: Mon, 1-Sep-86 22:40:59 EDT
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    Date: 25 Aug 86 11:25 EST
    From: davidsen%kbsvax.tcpip@ge-crd.arpa
    Subject: Toll Restrictor

    I would like to have a device to prevent outgoing long distance calls
    from my system. This will prevent abuse when rates are high. What I
    want is a box which will go between the modem and phone line, and
    monitor the outgoing tones. If the first tone is not a "1", the call is
    allowed, otherwise the line is disconnected.

My fraternity bought just such a device (against my advice) from a
electronics surplus place in Peabody, Mass. called BNR (I think).
Although the device does prevent people from inadvertantly using your
phone, it CANNOT stop someone who is intentionally trying to cheat you.

The device we got was an in-line passive black box that disconnected the
line if the first digit was one OR zero.  It was reset by the presence
of a dial tone.  By eliminating zero, people couldn't even use the phone
to make collect or credit card calls; they needed a Sprint account or
something.  This was no good, so I had to find a way around that.
So...there is now a sign over that phone that reads:

"To make a collect call: Depress the switchhook once rapidly, then press
 # + 02880 + area code + number."

Telecom readers should understand what's going on here.  Depressing the
switchhook once "dials" a one (remember pulse-code dialing?).  Pressing
the # deactivates the toll restrictor, but is otherwise ignored by the
phone company.  After dialing the rest of the sequence, you have
effectively dialed 10288 + 0 + area code + number, i.e. you have dialed
an AT&T operator-assisted call.

The above works, but anybody that understands the underlying reason can
figure out how to dial a long distance number.  Or, they can just ask
the operator when she comes on to complete the call for them, because
they were having trouble dialing or something.  To thwart this, your
device would also need to count pulses and disallow one or zero.  But a
person can usually call 555-1212 and have the information operator
connect you to an operator, or...

You can't win.  The best solution is to keep the phone under lock and
key.