Hello all...

I own a relatively late model Panasonic VCR. Last night I went to play a
tape (the VCR had been sitting idle for a while) and the picture came up as
mostly snow with good sound. I knew immediately that the heads probably
needed a good cleaning, so I took the VCR out and put it on the bench to
clean it up.

However, before taking it out, I noticed that the VCR was displaying an on
screen message stating that the heads probably needed to be cleaned and that
a cleaning tape should be used.

Now the video/audio/erase heads are clean and the VCR is working nicely.
However, I am wondering how the VCR "knew" that the picture quality was
poor? I don't think it was a simple timer-triggered event.

William