| 摘要 |
PURPOSE:To detect separate trouble easily by connecting a switching circuit at the node of a relay circuit and a load circuit while introducing an output from the switching circuit to a control circuit. CONSTITUTION:When an LED 622 cathode terminal for a photo-TRIAC 62 is grounded selectively at 0V by controlling a microcomputer 4, a repetitively pulsed signal corresponding to the frequency of a power supply 1 is transmitted over the input terminal 41 of the microcomputer 4. When either of heater circuits 31,...3n selected develops trouble and is in a nonconductive state, a high breakdown strength transistor 67 and a light-emitting device 681 are brought to an OFF state when the circuit is selected, thus supplying the microcomputer input terminal 41 with DC voltage at all times. Accordingly, the DC signal is transmitted over a transistor circuit 7 for driving a display circuit, and a light-emitting diode 73 is lit and trouble can be discriminated by visual observation. |
