| 摘要 |
In a system for receiving a scrambled pay television signal wherein a radio frequency video signal with a horizontal synchronizing signal erased therefrom by elevating portions of the video signal containing picture information and a radio frequency aural signal with a horizontal synchronizing trigger pulse and a data processing trigger pulse superposed thereon are received, the data processing trigger pulses are detected from the radio frequency aural signal and are used for comparison with a code assigned to a pay television receiving subscriber, and the horizontal synchronizing signal is restored on the basis of the horizontal synchronizing trigger pulses when the pay television broadcast is receivable; the improvement comprising a waveform shaping circuit which shapes the horizontal synchronizing trigger pulse and the data processing trigger pulse into desired pulse forms, a clock isolating circuit and a data isolating circuit to which the shaped pulses are applied and which deliver horizontal synchronizing pulses and data pulses respectively, a data comparator which makes the comparison by the use of the data pulses applied thereto, a vertical synchronizing signal-regenerating circuit which delivers a vertical synchronizing pulse, a gate circuit which is controlled by an output of the data comparator and which, when enabled, delivers a signal with the vertical synchronizing pulse added to the horizontal synchronizing pulse, and a switching attenuator which is controlled by the output signal of the gate circuit.
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