| 摘要 |
PURPOSE:To eliminate unstability of the characteristic of the decoder, by regarding only the case, where a predetermined number of positive and negative-polarity pulses from the limiter is continuous, as coming of the tone burst signal to perform the processing. CONSTITUTION:The signal is applied to signal period detector 25 and inverter 28 through limiter 23. The output of inverter 28 is applied to signal period detector 29. The signal from reference frequency oscillator 27 controlled by quartz oscillator 26 and the signal corresponding to the frequency of the tone burst are applied to signal period detectors 25 and 29. Signal period detectors 25 and 29 measure the timer length of the pulse signal, and output the output if it is within a determined range. The signal from signal detector 25 is applied to RSFF30 and monostable multivibrator 31, and the signal from signal period detector 29 is applied to RSFF30. Outputs of RSFF30 and monostable multivibrator 31 are applied to counter 32. |
