| 摘要 |
PURPOSE:To reduce the number of lead wires of cables and to handle a proximity switch easily by superposing an operation displaying signal to a cable at the operation of the proximity switch. CONSTITUTION:When a metallic substance 37 approaches close to a detecting coil 22, the oscillation level of an oscillation circuit 28 is reduced, a level discriminating circuit 31 generates an output, a transistor (TR) 34 is turned on through a current amplifier circuit 32 and a TR33 is also turned on simultaneously, so that a constant current circuit 36 is driven by a power supply. Consequently, DC current is made flow from the circuit 36 through a coaxial cable 26 and a light emitting diode 23 lights up. However, high frequency current continues to flow between the detecting coil 22 and a resonating capacitor 27 in respect of AC and the DC current component is superposed to the AC component. Thus, the operation can be displayed on the sensor head side without using an exclusive lead wire for the diode 23. |
