Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site nic_vax.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!uwvax!astroatc!nic_vax!brown From: brown@nic_vax.UUCP Newsgroups: net.consumers Subject: Re: Cable TV Message-ID: <135@nic_vax.UUCP> Date: Sat, 27-Apr-85 12:46:30 EDT Article-I.D.: nic_vax.135 Posted: Sat Apr 27 12:46:30 1985 Date-Received: Sun, 28-Apr-85 07:46:15 EDT References: <5250@tekecs.UUCP> <847@peora.UUCP> <134@nic_vax.UUCP> <860@peora.UUCP> Organization: Nicolet Instrument Corp. Madison WI Lines: 44 > (1) My cable tuner is a "dumb" tuner, not one of the new digital ones; > the inside looks like a typical TV tuner, and tuning is done through a large, > unwieldy box with a slide switch that selects one of a number of > potentiometers mounted on a PC board inside the box. Thus I don't think > they are sending it commands from outside to program it. I just tried calling your cable company, but since it is only Saturday, Customer service is the only ones there. To find out for sure I will have to call on Monday and ask an engineer there. But, from your description I believe the following. That same kind of box is used by two different cable companies around here. One of which IS addressable from the main plant. The unwieldy box selects the channel, but the other circuitry determines if you are allowed to receive the pay channel or not. If the system is not addressable (like the other cable system around here), there is an extra board inside of the channel selection box that has resistors on it. Some are shorted some are not. If the resistor is shorted out, then no pay channel restoration takes place. If the short is cut, so that the 680 ohm resistor is again in the circuit path, the pay channel connected to that resistor is restored. If there are channels 2 thru 36 on the box, there are that many resistors. This method would be used for your pay channels of Cinemax, Showtime and Disney. As for HBO, it sounds like they use a filter to remove the main vision carrier. That is the method used in my cable system and one of the others. That way, the signal is sent down the cable unscrambled, for the best possible picture. The sine-wave-sync suppress system, in my opinion, is the worst method ever devised for scrambling. It causes gain riding that shows up in the picture as a band of clean and noisy picture areas. If you have a video deck, just hook up the scope to the video output and dial up a channel that has a pay channel, other than HBO. You should see a sine wave riding on the signal, either at the 15750 Hz rate or at the 31500 Hz rate. The Horizontal sync pulse will be riding on the positive peak of the sine wave. > (2) When I discontinued HBO, they did not have to come inside to turn on > the scrambling for HBO. Reason for that mentioned above. This discussion could go on forever, but I'm sure we don't want it to. I will call your cable company on Monday as find out what I can and post it to the net. If anyone as the answer, they sure must. Mr. Video