| 摘要 |
<p>PURPOSE:To obtain an automatic stop signal of high reliability with a simple constitution by using two different frequencies as the stop signal in a learning machine, etc. CONSTITUTION:An automatic stop signal consisting of two signals F1,F2 of different frequencies like (a) is beforehand recorded in the specified position on the audio signal track of a recording medium 1. At the reproducing, the audio sigal of the recording medium 1 is reproduced through a magnetic head 2, preamplifier 3, main amplifier 4 and speaker 5. When the automatic stop signals F1,F2 are detected, the signals F1,F2 are subjected to waveform shaping through BPFs 6, 6a which allow the passage of only the respective frequencies, rectifying circuits 7, 7a, integrating circuits 8, 8a, waveform shaping circuits 9, 9a, etc., after which they are respectively inputted to the set-reset terminals S, R of PSFF10. The output of the FF 10 is supplied to an AND G1 and monostable multi 11 and further the stop instruction signal is generated by an AND gate G2 for the time necessary for operating the monostable multi 13 and stopping the reproduction operation in a counter which counts the pulses of the preset number.</p> |
