| 摘要 |
<p>PURPOSE:To minimize the occurrence of a click sound when a call electric current channel from a telephone exchange is reversed by providing a semiconductor amplifying element serially connected between a photo coupler and an operational amplifier. CONSTITUTION:An earth electric potential point 41 and a -48V electric power source terminal 42 go to be a telephone exchange call electric current electric power source, a connecting point 43 of semiconductor elements 12 and 13 is connected to the input terminal of an operational amplifier 31 and the terminal such as a telephone set is connected between telephone circuit terminals 1 and 2. When a control signal is given to terminals 29 and 30 and both photo couplers 26-1 and 26-2 light up, the semiconductor element 13 goes to be an action condition, and the accumulating charge of a capacitor 21 passes through the element 13 and discharging is started. By selecting the semiconductor element 13 and resistance 51 and 52, the electric potential of the connecting point 43 descends in a straight line from when the photo coupler 26 is turned off, a high harmonic component included in the waveform of the reversing signal is minimized and the noise generated is also minimized.</p> |
