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From: U5434122@ucsvc.ucs.unimelb.edu.au
Newsgroups: comp.dcom.telecom
Subject: Payphones and DTMF Dialling
Message-ID: <15531@accuvax.nwu.edu>
Date: 20 Dec 90 23:35:20 GMT
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X-Telecom-Digest: Volume 10, Issue 892, Message 8 of 9


As I described earlier, Telecom Australia has begun installing debit
card telephones, which have fancy LCD displays and pushbutton keypads,
instead of rotary dials (my, we are backward, aren't we.)

I have been trying to discover why these payphones do not have DTMF
dialling enabled.  I accosted an installer yesterday and grilled him
as much as he could take.  The payphones *do* have DTMF capability (I
saw the internal switch) but orders are that all are to be left on
'pulse'.  I asked for a reason.  First reason was that the exchange
did not have DTMF enabled.  I pointed out that the phone was connected
to the 899 exchange which is totally computerised, and thus DTMF was
available on all lines.  The installer answered that it is there "at
customer request, and we (TA), as the customer, don't want it."

On further grilling, it appeared that TA was afraid of fraud, and so
disables DTMF from all payphone lines (except those of COCOTS whose
owners ask for it.)  The latest COCOT, the Blue Phone, apparently has
some sort of device which prevents fraud from being perpetrated
whether DTMF is enabled or not.  Or perhaps TA just charges the owner
for all calls anyway.  What TA is afraid of, I believe, is someone
(lots of people) with tone senders, available from the major banks,
coming along and bypassing the payphone's dialling system to place
calls.

What I would like to know is: How do the American and Swedish telcos
avoid fraud of this type? (They are the only two countries I
personally know to have DTMF payphones. Comments from elsewhere are
also welcome.)  Is it possible to use a tone-sender to dial from a
payphone in USA or Sweden or elsewhere?

If this is indeed TA's worry, how effective would such a simple fix as
disabling the handpiece microphone until answer supervision be?  The
phones *do* listen for answer supervision: they must as they don't
take your money or card-credits until the call is supervised.

Help appreciated, (I shall summarise and post e-mail in the New year.)

Thanks,

Danny

u5434122@ucsvc.ucs.unimelb.edu.au  
Above is IMHO.  Nothing to do with Telcom Australia, or Uni. of Melbourne


[Moderator's Note: Disabling the mouth until supervision would prevent
the phone from being used to call directory enquiries or the operator;
both of whom answer unsupervised, no?  PAT]