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From: Peter_Warren_Lee@cup.portal.com
Newsgroups: sci.electronics
Subject: Answering Machines
Message-ID: <31790@cup.portal.com>
Date: 16 Jul 90 23:19:37 GMT
Distribution: na
Organization: The Portal System (TM)
Lines: 12

Being a hopeless paranoid type of person, I have a question about answering
machines that can be accessed remotely by a 1-4 digit code that you press
in on any touchtone phone...
 How do the circuits work that detect which buttons are being pressed?
Do they just check to see if the correct tone is present or do they also
check to make sure that ONLY the correct tones are present?
 For instance, would these systems be safe against someone with a seven 
tone generator that sent out all the tones at the same time that the phones
normally use for dialing?
Thanks,
                                  Pete
  Peter_Warren_Lee@cup.portal.com