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The Telecom Digest for December 10, 2010
Volume 29 : Issue 333 : "text" Format

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Re: Question about an old scrambler phone(Lisa or Jeff)

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Date: Thu, 9 Dec 2010 09:49:55 -0800 (PST) From: Lisa or Jeff <hancock4@bbs.cpcn.com> To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org. Subject: Re: Question about an old scrambler phone Message-ID: <2a2a0895-c61d-43cc-8ab1-560298fcb3f2@h22g2000vbr.googlegroups.com> On Dec 8, 7:38 am, bon...@host122.r-bonomi.com (Robert Bonomi) wrote: > One of the simplest forms of a 'scrambler' simply frequency-inverted > the audio input. basically, use the audio to AM modulate a circa > 4kHz 'carrier', and send only the the lower sideband over the > wires.. When the Bell System introduced overseas communications via radio, they included frequency shifting as a privacy measure. It was more designed to prevent inadvertent evesdropping as opposed to stringent security. They said a person with excellent hearing and skill could listen the discern the conversation, and of course constructing a descrambler would not be hard to do. It's written up in the Bell Labs history.
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