| 摘要 |
<p>PURPOSE:To detect a running speed during reproduction being different from that during recording by providing a reproducing means which reproduces a video and a pilot signal and a detecting means which detects variations of the pilot signal and a playback output. CONSTITUTION:A tracking control signal from a demodulating circuit 12 is supplied to a capstan servo circuit and also led to BPFs 15 and 16 which allows only signals having a two-frame and a four-frame period to pass through them, and only their frequencies are extracted and detected by detectors 17 and 18 to obtain DC signals. Their detection output signals contain even simple noises, so they are averaged by integration circuits; only when the mean values exceed a preset threshold voltage E2, outputs A and B go up to a high level H. The H-level output A shows the standard speed reproduction of a tape recorded in long-time mode and the H-level output B indicates the long-time mode reproduction of a tape recorded in standard mode. The outputs A and B are inputted to a switching control circuit 27 to controls the tap running speed according to the outputs A and B.</p> |
