KLUDGE@AGCB8.LARC.NASA.GOV (Scott Dorsey) (03/15/90)
One of the older copy protect systems used on VHS tapes was a very low
frequency (1 to 5 Hz) component added to the video signal, which would
have a tendency to mess up the synch stuff on video recorders, as well\
as overdriving the heads. It didn't work very well, everybody bought
small high-pass filters to defeat them, and it's probably still being
used somewhere. Unfortunately, it would mess up a number of television
sets, as well.
Disclaimer: I don't do video. I don't even own a TV set. I do have a
two-projector 16mm rig in my living room, though.
--scott