On some movies that are on VHS, there is a quick series of tones that sound similar to those on a touchtone phone. What are they for? Are they related to the tones are sometimes heard on broadcast cable TV?
Thanks.
Some tape duplication processes involve adding electronically-readable cue signals to the start of the tape being duplicated. These are sometimes also audible. The cue signal goes through the distribution amps that power and supply the banks of copying machines, so that they all start at the same time. There may be similar signals at the end so that they all stop at the right point as well. Sometimes, these signals are also audible when you play the copy.
Why make the cue signals audible to the human ear? Sometimes it’s handy for the engineer geek who is setting up or running the copying banks.