Xref: utzoo misc.consumers:14192 misc.misc:8392 sci.misc:3855 sci.electronics:8309 Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!cmcl2!lanl!opus!ted From: ted@nmsu.edu (Ted Dunning) Newsgroups: misc.consumers,misc.misc,sci.misc,sci.electronics Subject: Re: Telephone privacy gadgets Message-ID: Date: 24 Oct 89 00:07:45 GMT References: <799@mccall.uucp> <776@ariel.unm.edu> <397@hq.af.mil> <20247@mimsy.umd.edu> <1917@dover.sps.mot.com> Sender: news@nmsu.edu Followup-To: misc.consumers Organization: NMSU Computer Science Lines: 27 In-reply-to: waters@darla.sps.mot.com's message of 23 Oct 89 17:51:36 GMT In article <1917@dover.sps.mot.com> waters@darla.sps.mot.com (Strawberry Jammer) writes: Audio scrambling using analog means is very easy to break as a result, digital scrambling can be made extremly difficult but requires 3-4X the bandwidth of the telephone line (2.5Khz Vs 16Khz). Not something you can use from your home or office. this comment about bandwidth is inaccurate in these days of 9600 baud modems. adaptive delta modulation can transmit very reasonable speech over less than 9600 bits per second and encryption at this rate is not difficult with dedicated hardware (and probably not out of reach for something like a mips or sparc processor in software). vocoder techniques can reduce the bit rate requirements to approximately 2400 bits per second, but you tend to buy back the sophistication of the modem with the sophistication of the coding for the speech. -- ted@nmsu.edu Dem Dichter war so wohl daheime In Schildas teurem Eichenhain! Dort wob ich meine zarten Reime Aus Veilchenduft und Mondenschein