| 摘要 |
PURPOSE:To obtain a stable DC detection signal without distortion, by detecting an AC ringing signal with a monostable multivibrator. CONSTITUTION:When a ringing signal A from main trunks 6a, 6b is applied to a ringing signal reception circuit 5, a rectifying circuit consisting of diodes D1- D4 makes full-wave rectification for the said ringing signal A and the result is applied to the input side of a photo coupler 1. The output of the photo coupler 1 is a rectangular wave as shown in waveform B and inputted to a monostable multivibrator 1 as a trigger signal. As a result, the monostable multivibrator 1 outputs a detection signal as waveform C. The output pulse width Wp of the monostable multivibrator 1 is set slightly wider than the width Wt of a trigger signal B. |
