| 摘要 |
PURPOSE:To attain the accurate decision of an information signal even in case a magnetic head has no accurate tracking, by superposing a low frequency signal having a small azimuth loss on the information signal for recording, extracting the low frequency signal in a reproduction mode to compare with a reference potential and therefore deciding the presence or absence of the information signal. CONSTITUTION:The low frequency signal supplied from a low frequency signal input terminal 6 of a magnetic recording/reproducing device is superposed on the information signal sent from an information signal input terminal 7 at the preceding stage of a record amplifier 8. Then an LPF9 is set between a reproduction amplifier 2 and a wave detection circuit 10 for extraction of the low frequency signal out of the superposed signal. This low frequency signal is turned into a signal having a small azimuth loss of a prescribed frequency band and recorded on a magnetic tape by a rotary head 1. Then the low frequency signal is extracted through an LPF9 in a reproduction mode and supplied to the circuit 10 for envelope wave detection. A comparator 11 compares the wave detection output with a reference potential, and an output signal is outputted to an output terminal 5 in accordance with the presence or absence of a recorded signal.
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