Method for producing copy protected recorded videotape having uncopyable vertical synchronizing signal partition

A method of recording video signals on a first videotape to allow display of video picture information on a television receiver having a synchronizing signal separating circuit, the method preventing playback from a second videotape made from the first videotape on a videotape machine, the method comprising the steps of:

• generating a video signal train corresponding to a television signal train from a video information source, said video signal train comprising video picture information and a composite synchronizing signal in a vertical blanking interval to control the picture field and frame, the composite synchronizing signal including a first equalizing signal partition, a vertical synchronizing signal partition, a second equalizing signal partition and a horizontal synchronizing signal partition;
• and
• encoding the vertical synchronizing signal of said video signal train by:
• forming a vertical synchronizing pulse having a pulse width of 1-20 micro-seconds and a pulse height discernible by a vertical synchronizing signal separating circuit of a television receiver,
• reducing a signal level of the vertical synchronizing signal partition, except for said vertical synchronizing pulse, below a pedestal level of the television signals, and
• reducing a signal level of the second equalizing signal partition and at least a part of the horizontal synchronizing signal partition below the pedestal level of the television signals, said encoding enabling display upon receipt of the resulting encoded video signal train by a television receiver, said encoding preventing normal operation of the vertical synchronizing signal separating circuit of the television receiver if the encoded signal is copied to said second videotape;
• and
• recording the encoded video signal on a blank videotape.