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From: cgordon@vpnet.chi.il.us (Gordon Hlavenka)
Newsgroups: sci.electronics
Subject: Re: Descramble Cable Using Filter?
Message-ID: <26912307-29c.5sci.electronics-1@vpnet.chi.il.us>
Date: 4 Jul 90 01:55:04 GMT
References: <3525@umbc3.UMBC.EDU> <866@ssc.UUCP>
Lines: 13


ON-TV used a system (back in the goodle days...) where the sync pulses were
attenuated.  The sync information was then AM'd as a sine wave onto the FM
audio subcarrier, which in turn was in a non-standard location.  You had to
retune the audio tank, recover the sync, phase shift it by some amount,
integrate it, then mix the spikes back into the video.  The easier-to-build
boxes had their own audio and speaker; you just turned the volume down on
the TV...

Nowadays, of course, most of this scrambling stuff is done with digital
encryption, or at least digital access to the descrambler box.
----------------------------------------------------------
Gordon S. Hlavenka                 cgordon@vpnet.chi.il.us
Disclaimer: He's lying