PURPOSE: To reduce the delay in a time to detect a calling of a subscriber by flowing a standby current between an anode and a cathode of a semiconductor switch of PNPN four-layer structure.
CONSTITUTION: The 1st ∼ 4th semiconductor switches Q1∼Q4 having the 1st live terminal 1, the 2nd live terminal 2 and a gate 3 are provided. In fiqure, N is a DC power supply circuit and T is a telephone set. A transistor (TR)Q5 is connected between the cathode of the 1st semiconductor switch Q1 and the anode of the 2nd semiconductor switch Q2 and the 5th current source I5 is connected to the base. I1∼I4 are current sources connected to each gate of the semiconductor switches Q1∼Q4. Thus, the turning-on of the semiconductor switches is quickened and the time delay to detect a calling of the subscriber is reduced.
TANABE MASAAKI
KIMURA TADAKATSU
Next Patent: JPS6020628