| 摘要 |
PURPOSE:To reduce the size of an automatic decision device for a noise reduction system by recording a modulated signal obtained by modulating a carrier signal below the audio frequency range according to the kind of the noise reduction system on the same track with recording information. CONSTITUTION:When, for example, a noise reduction system (NR system) NR2 is selected during recording, an amplitude modulator 3 imposes amplitude modulation on the carrier signal from an oscillator 4 with a modulating signal of 1Hz to obtain the amplitude-modulated signal. This signal is recorded on the L channel of a magnetic tape together with a recording signal and on the R channel together with the recording signal after being inverted in phase by an inverter 6. Then, only identification signals are extracted from reproducing signals picked up by reproducing magnetic heads LPH and RPH from the L and R channels. Identification pulses obtained from the identification signals are supplied to period detecting circuits 13a-13c. Those detectors measures respective periods of the identification signals and performs switching control over a suitable NR system through a control circuit 14. Thus, the device is reduced in size. |
