Aucbvax.1349 fa.human-nets utzoo!duke!mhtsa!ucbvax!DERWAY@MIT-ML Thu May 14 22:03:01 1981 HUMAN-NETS Digest V3 #100 HUMAN-NETS AM Digest Friday, 15 May 1981 Volume 3 : Issue 100 Today's Topics: Query Replies - WHT and Cable & No Calorie Sugar ---------------------------------------------------------------------- Date: 12 May 1981 12:43 cdt From: Phinney at HI-Multics (Tom Phinney) Subject: Question about WHT and cable WHT apparently uses the same technique as other companies in the pay-TV trade. The video signal is "scrambled" by mixing the true video with a sine wave phase-locked to the video's horizontal line rate, 15734 Hz. The sine wave has its greatest amplitude at the left edge of the "line" of the true video signal, which is where the line sync information is normally found. Line sync is determined by the lowest amplitude point in the video signal, so adding this phase-locked sine wave causes the TV circuitry to locate a false sync somewhere in the middle of the normal picture. This causes the displayed picture to be rotated by about half a screen width, more or less depending on the amplitude of the original mid-screen video information. The sound is "hidden" by using a technique similar to the "storecasting" approach used by many FM stations -- a high-frequency subcarrier (87 KHz if I remember correctly) is added to the normal audio, which in your case is the pay-tv advertisement, and the desired audio signal is used to FM modulate that subcarrier. This means that the received signal must be demodulated twice to recover the "hidden" audio, once to recover the video and wide-band audio, and a second time to recover the "hidden" audio. As I recall, the 15734 Hz sine wave is also mixed with that recovered audio signal (and filtered out by a low-pass filter in your TV receiver), so that the pay-tv decoder just mixes the recovered sine wave (inverted) with the video signal to unscramble it. Home-made decoders to unscramble these signals are possible, and are fairly easy if your TV is old enough that the available signals are not buried inside an IC. In that case you can make a demodulator with about five ICs, and put it inside your TV. Otherwise you have to add the RF front-end to the system, and that's a fair amount of trouble, because you need to supply some form of AFC (automatic frequency control) to the UHF front end to get stable reception on the channel. There are people in most of the major semiconductor manufacturing areas (Silicon Valley, Phoenix, Austin) who make these decoders as a side business, and you might be able to locate one through local residents. Otherwise check out the local pirate-tv outlet in your neighborhood. The cable TV guys hate the pirates and sue them all the time, so don't look for a listing in your yellow pages. I hope this has helped a little. Tom Phinney ------------------------------ Date: 12 May 1981 00:05:58-PDT From: ihnss!karn at Berkeley Subject: Pay TV decoders I believe the Channel 68 pay TV scheme in use in Northern NJ is ON-TV, the most famous of the over-the-air subscription TV systems. ON-TV is being run over Channel 44 here in Chicago, and a number of us have built decoders to receive it. This is how the signal is encoded: The modulated video carrier is itself amplitude modulated with a 15734 hz sine wave phase locked to horizontal scanning. The sine wave is phased such that the horizontal sync pulses occur in the "valleys" of the sine wave. Since horizontal sync is normally supposed to occur at maximum carrier level, the TV set (without decoder) triggers on random video in the middle of the scan line. Thus you get the wavy vertical black bar (horizontal sync) down the center of your screen. The same sine wave is also amplitude modulated on the sound subcarrier (remember, the sound carrier is normally only frequency modulated with the sound, so the two don't interfere.) The decoder must amplitude demodulate the sound carrier, filter the sine wave, and AM the received video signal, usually by sending it back into the receiver's AGC stage. Note that phase locked loops won't work, as the sine wave is gated off during the vertical interval. The sound is placed on a 63 khz FM subcarrier, which in turn modulates the main FM sound carrier. This technique is identical to the SCA system used by FM broadcast stations to transmit MUZAK or similar worthless programming. The sound is easily received with a 565 PLL or equivalent at the sound discriminator output. The audio "baseband" is available for use as a "barker" channel ("Look what you're missing by not being an ON-TV subscriber..call 555-1212, etc") but it isn't used here except for hourly station ID's. There are a rapidly increasing number of companies selling boards and kits for ON-TV decoding. They are NOT selling, for the most part, completed, working units, as this keeps them out of trouble (especially in California). Phil ------------------------------ Date: 05/11/81 07:38:49 From: PCR@MIT-MC Subject: left handed sugar I don't know about the rest of you, but I was reading about left-handed food and how it wasn't any good for nutrition 10-15 years ago. The idea is an old standard in science fiction. ...phil ------------------------------ Date: 10 May 1981 09:16-EDT From: Robert Elton Maas Subject: No-Cal Sugar (1) The use of the term "natural" for this mirror-reverse of sugar (sucrose??), and the claim it's chemical identical to normal sugar, are abuse of the language. Most of the biological mechanisms for processing food and other chemicals in the body are specific to the handedness of the chemical being processed. I'm not a biochemical expert, but I would guess a lot of processing sites in the body would get confused by this un-sugar, perhaps "recognizing" it as some other chemical and attempting to perform chemical transformations on it that weren't appropriate. I'd think that detoxifying mechanisms would have trouble with it, and it could easily be cancerous. Can some biochemical expert speculate further? (2) There have long been science fiction stories about somebody traveling around the universe or through some broken transporter device and coming back reversed and starving because all the food was backwards for this traveler. Looks like sci-fi has started to become reality. Soon (30 years?) we'll be making complete DNA and life in reverse, growing food that only reversed creatures cn eat. Imagine the CIA arranging that wheat we sell to the USSR is reversed. It bakes nice looking bread that doesn't support life. I wonder why reversed sugar tastes sweet? Does the tongue measure just the gross chemical characteristics instead of looking specifically for sugar compounds? (For salt and sour tastes it obviusly does just measure ionic charge balance or somesuch. But bitter and sweet I don't know about.) Would reversed-wheat taste like wheat, or are smell receptors more sensitive to handedness? (3) Some of that probably is outside the subject of HUMAN-NETS, but I'm not sure it belongs in SCI-FI-LOVERS either. Oh well. Someday we'll have a real HUMAN-NET with threaded multi-term indexing and keyword profiles for each user, instead of discrete mailing lists... maybe. (4) Reverse-handed sugar has been known for decades. How can anybody patent it? It must be some commercially feasible way to make it that got patened, not the chemical itself, right? ------------------------------ Date: 10 May 1981 (Sunday) 1110-EDT From: MOSESJ (Jack Moses) Subject: no-cal sugar....an uninformed opinion The "L" stands for the Levo-rotary isomer of sucrose which, when passed through a Polarized filter, will cause light to turn to the left (rather than the commonly occuring dextro variety which turns light to the right). The isomeric properties of most compounds is an extablished fact; thus one must conclude that since L-sugar does exist in nature, it would be ludicrous for the agency to issue a patent on a naturally existing substance. The patent must have been issued for the PROCESS that created the substance; and therein lies a formidable problem. In organic chemistry a slight alteration of the flowchart sequence will allow competitors to produce the compound without infringement. So much for the value of the patent itself. I am not in a position to pass judgement on the medicinal, social or economical value of the L-sugar itself, not having any info on same, but the value of the isomeric properties is exemplified in the example of a familiar (to most of us) Eli Lilly product known as Darvon. In it's Dextro-rotary form, Darvon in a non-narcotic pain reliever which acts on the synapse of certain nerves associated with pain, thus producing relief. But when Lilly made a Levo-rotary isomer of the same compound, it acted on the sinus node to inhibit the production of histamines, thus offering relief from colds. This product was appropriately named NOVRAD (Darvon backwards) .... an antihistamine. So much for the organic stuff....now if the subject matter was regarding the stock market (that is my REAL bag) drop me a line. Jack ------------------------------ Date: 11 May 1981 0744-PDT Subject: No-Cal Sugar From: ADPSC at USC-ISI (1) I agree that the term "natural" is a bit overused. If we are to use the broadest definition, then anything could be called natural. It is one of those terms which I have begun to more or less ignore in its usual context, assuming that the term desired was "organic". Perhaps Edwin Newman will choose to deal with this one if he hasn't already. (2) It appears that just the process for producing this "new" sugar was patented. Knowledge of these substances has been around for many years. The problem arose in trying to find commercially feasible production methods. Apparently Biospherics feels it has found such a process. I read most of the article as so much hype. (3) From what little I know of sugars (not being a biochem-type), and from what my friends have been able to get through to my non-biochem oriented brain, "normal" and the "left-hand" sugars might be (very simplistically) pictured as: A B A Normal CCCCC Left CCCCC B The body recognizes the A's and C's in taste, but looks for the B's only in digestion. As a friend of mine put it, other things often get mistaken for sugars, but sugars seldom get mistaken for much else. As such, the potential for causing cancer is minimal. Again, not being a biochem-type, I don't know how bacteria reacts to this stuff, so I can't form a good opinion on the tooth decay issue. (4) The problem of applicability of mailing list of course exists. Too much stuff doesn't seem to fit adequately into HN or SFL. I'm open to any suggestions on that one. Don ------------------------------ End of HUMAN-NETS Digest ************************ ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.