Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!newstop!exodus!oobleck.Eng.Sun.COM!bender From: bender@oobleck.Eng.Sun.COM (memory fault - core dumped) Newsgroups: sci.electronics Subject: "spiking" of cable-TV descramblers Message-ID: <13867@exodus.Eng.Sun.COM> Date: 23 May 91 04:39:00 GMT Sender: news@exodus.Eng.Sun.COM Distribution: na Organization: Sun Microsystems, Mt. View, Ca. Lines: 57 Sometimes, I'm amazed at the lack of a sense of humor on some of the newsgroups on the net. For example, below are some excerpts from two articles that I posted to rec.video concerning cable company "spikes" to disable (illegal) descrambler boxes. I posted them in direct response to the fairly large amount of postings concerning descramblers that don't work any more. Now, perhaps I'm mistaken, but I don't see how anyone with an even rudimentary knowledge of video and electronics could have taken my postings seriously, but it seems that many people did, since I've received countless e-mails ranging from "You're an idiot" to fairly detailed dissertations about how the horizontal retrace interval can't POSSIBLY be synchronized to the zero-crossing of the AC line, as well as some "learned" opinions that cable TV distribution amplifiers (those mounted outside on the poles or buried underground) wouldn't be able to pass 50,000 (or 20,000!) volts!! I figured that the "four 5Kv neon sign transformers wired in series" part of my second posting would have given this away as a farce, but apparently not. Maybe I should have included some :-)'s??? >That's not what I heard! I heard (from a FOAF no less!) that the cable >company does indeed send a "spike", but it's during the horizontal retrace >time, so that normal TV's and VCR's won't be affected. The spike is around >50,000 volts with a duration of 20 mS, and is repeated eight times during >the prime-time viewing hours from 8PM until 11PM EST (so that west coast >viewers will of course receive the spike between 5PM and 8PM). Because of >the necessarily high voltage of the spike, it leaks over into some of the >unused cable channels; if you have a Toki Industries CDV-4000 addressable >decoder, you can tune it to channel 85 or greater, and observe the spike >intermixed with the "snow"; the reason that you can see the spike on an >unused cable channel is because unused channels have supressed sync pulses, >and so the AGC in your receiver will be operating at maximum gain, and so >will be able to pick up the 4th and 5th harmonics of the spike that is >transmitted on the lower-frequency cable channels. What the spike does is to >fuse several of the memory locations in a cable converter boxes' ROM (the >chip that provides the instructions as to which channels to receive and >block); by fusing these locations they appear as hex 0x0FF to the converter >descrambling circuitry, which is an invalid channel combination, and so the >converter box goes into an endless self-diagnostic mode, in which none of >the scrambled channels can be descrambled.