SIGNAL TRANSMITTING CIRCUIT

PURPOSE:To prevent malfunction due to noises by connecting plural transistors (TR), which turn on by the output current of a photocoupler, in series. CONSTITUTION:The signal from a control circuit is transmitted to a gate circuit by using a photocoupler 1. Under the ''on'' command from the control circuit, a current flows through a photodiode and then a photocurrent flows between the collector and base of the photodiode to turn on TRs 2 and 4. The conduction of the TR4 turns on a TR2' and an output TR7 turns off. Unless the TRs 2 and 4 both turn on even when either one turnes on by a noise current i1 or i2, the TR7 never malfunctions.