| 摘要 |
A copy protection arrangement for pre-recorded videotape cassettes. The invention includes both a method of protecting and a protected videotape cassette. Copy protection is provided by recording on at least a portion of the original videotape a composite synchronizing signal including a vertical synchronizing pulse having a pulse width in the range of 1-20 micro-seconds and a pulse height discernible by a vertical synchronizing signal separating circuit of the television receiver. All other vertical synchronizing pulses in the vertical synchronizing signal partition, all the equalizing pulses in a equalizing signal partition following the vertical synchronizing signal partition and at least a part of the horizontal synchronizing pulses in a horizontal synchronizing signal partition following the equalizing signal partition in the composite synchronizing signal have respective pulse heights less than a predetermined pedestal level of the synchronizing signals.
|
