Path: utzoo!censor!geac!jtsv16!uunet!wuarchive!texbell!attctc!mjbtn!raider!crc
From: crc@raider.MFEE.TN.US (Charles Cain)
Newsgroups: sci.electronics
Subject: Re: automatic commercial deletion
Summary: Tones are used for cable system headends (LONG)
Keywords: commercials, compressors, VCRs, film editting
Message-ID: <137@raider.MFEE.TN.US>
Date: 21 Sep 89 20:54:41 GMT
References: <6428@ingr.com> <11213@fluke.COM>
Distribution: usa
Organization: RaiderNet Public Access, Murfreesboro, TN
Lines: 38


The way that most of the networks like ESPN, TNN, A&E, etc.,etc., use what
is called Monroe tones. These are tones that are transmitted over a subcarrier
over the satellite to the cable systems. Each cable operator has to buy their 
own decoders. The tones that you hear on ESPN whenever they go to a break is the
monroe tones being sent. TNN, for whom I work, sends out their tones 8 seconds
before going to black. This gives the cable system tape machines time to come upto speed and color lock before the MC switcher takes the machine online.

The big 3 networks do it somewhat differently. NBC has the capability to auto- 
mate the system by using a SCPC carrier that is broadcast along side the main
satellite signal. This carrier can switch receivers, move the dish, ANYTHING 
they at NBC Master Control want it to do. CBS and ABC are still doing it the
hard way. The way that they tell the affiliates to go to a break is by throwing
up a slide or still store and saying,, """""""""""", 'This is CBS' or 'This is ABC'. CBS is
working on a similar package as NBC but have not as yet implemented it nation-
wide.

But all of this is for naught if a station decides to block a network promo
or commercial with their own. In that case, their is no way that I can think
of that a 'commercial killer' could pick it up, unless it looked for a timing
shift from one signal to the other, or looked for compressed audio, which 
commercials are HIGHLY compressed to create the effect of louder and hence
get your attention. This last method would probably be the best way to have
something know it was receiving a commercial and do a backspace edit to last
black and pause the recorder.

I hope that this helps somewhat. I apologize for the length of the post. If
anyone has any more questions, please email you questions to me.

Randy Cain

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DOMAIN: crc@raider.mfee.tn.us     |	      From NASHVILLE, TENNESSEE     
Satellite Engineer, TNN           |           Home of the Grand Old Opry!
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