| 摘要 |
PURPOSE:To enable stable interruption of echo signal and normal signal without requiring external reset signal, by detecting the point where a variable threshold value is greater than the maximum value of signal, storing this detected signal with effective output information from a receiver, and compulsively restoring a logic control circuit section. CONSTITUTION:A comparison circuit 39 compares the input signal (k) of a rectifying circuit 38 with a variable threshold voltage (l), and the output (m) of rectangular wave pulse train is absent when the level of the signal (k) and the voltage (l) is inverted. A rectifying circuit 40 converts the output (m) into a DC pulse a given time after the pulse train is absent. A storage circuit 34 is made storable with an effective input signal and stores the interruption information of echo and normal signals, and takes the logical product between the inverted output of the circuit 34 and the logical gate input rejection signal (e) in a hold logic circuit, and the output is fed to the hold logic circuit as a compulsive interruption signal. When a receivers is restored, the output information of the receiver is inverted and input to the circuit 34, to erase the stored content. |
