| 摘要 |
<p>In a system for monitoring use of a video monitoring system, RF signals are injected into a cable converter (26) and a VCR (24) in order to detect channels selected by the cable converter (26) and VCR (24). Installation of probes is not required for channel detection. Channel identification signals are also injected into the VCR (24) and cable converter (26) for recording by the VCR on videotape. Respective channel identification signals are provided to the cable converter (26) and VCR (24) is determined by injecting a code signal into the VCR (24) with time multiplexing. The state of the 'TV/VCR' switch of the VCR (24) and determining whether that signal is present in an RF video signal output by the VCR (24). The system includes a switch for interconnecting the cable converter (26), VCR (24) and T.V. (22) and also for coupling injection signals to respective inputs of the cable converter (26) and VCR (24).</p> |
