It had to do with screwing around with the vertical blanking interval. TV's had no issue with it, but VCR's would fail.
Cable TV "scrambling" was similar back in the day as well. It wasn't so much that the signal was "encrypted" as it was "modified" in such a way it wouldn't play on a normal tv anymore. Over time they could modify the scrambling technique so that any box you did buy to descramble a signal would be worthless in a few months when they changed the method.
The only way to really descramble Pay TV was to be an electronics guy who could reconstruct the video signal. Usually you needed the minimum of an oscilloscope to analyze the timing signals, and then the ability to create a circuit to fix it -- it wasn't exactly easy.
In the early 80s where I lived, there was some kind of filler that, once removed, allowed you to watch HBO. It was housed in a green box exterior to each house, where the cable left the street and entered your house.
I don’t know if it was a filter really. It was just an electronic component of some kind that screwed on/off.
When you ordered HBO, someone visited your property to remove this thing.
Back when TV stations were broadcast on frequencies, it would be as simple as a notch filter to block out that particular frequency that HBO/Skinemax was on.
I'm guessing it was something like a jumper over an AGC (auto gain control) circuit VCRs use to avoid saturating the tape, since the MacroVision mechanism was basically to intermittently blast out-of-frame lines with too-intense brightness, which has no effect on a typical TV, but does make the AGC clamp down so the whole frame is intermittently too dark.
Ah yes, crude indeed. We used to cut a small piece of payer, around an inch. Then fold it into a little square and place it inside that little empty square space on the front of the cassette tape. That's all it took to subvert it.
By the way this worked just as well for audio cassettes tape.
As sidpatil says, that's a write-protect tab. If you bought blank VHS tapes and recorded something you could rip the tab off to stop you or someone else accidentally overwriting, say, your wedding video. Of course, all retail tapes were tab free.
And you could simply use masking tape to bypass it, because it was only designed to stop unintentional overwriting, not intentional overwriting.
I'm pretty sure as a kid I wrote over a few (bad) retail VHS movies this way, tapes that served more value as blanks.
>I'm pretty sure as a kid I wrote over a few (bad) retail VHS movies this way, tapes that served more value as blanks.
Now that I think about it, I've never gotten a Blockbuster/Hollywood Video rental that was damaged in this manner. This method of property destruction never even crossed my mind. It seems so obvious given how easy it is to disable write protection. Was I just lucky or were people more considerate back then?
Just to clarify, I meant retail tapes I (read: my parents) owned. I never overwrote rented tapes.
I recall rental shops would have rewind machines, but I don't remember them ever checking the content of the tape.
Maybe people were just considerate. Maybe the threat of having a whopping fine when the the next unhappy renter returned and complained about the tape, causing the shop to check the rental history, dissuaded such behaviour.
Or, maybe people respected the institution. I used to really like video stores as they offered affordable access to entertainment and were just nice places to visit.
