| 摘要 |
<p>A plunger is drawn into one or other of two coils, energised as required. Three wires connect these coils to a monitor circuit giving visual indication of the instant switch position. Each coil is connected to an oscillator circuit consisting of a transistor (T1) a tuning capacitor (C11), decoupling capacitors (C13,C14) and rectifier diodes (D13,D14) working into a load resistor (R15). The output voltages across the load resistors (R15,R25) of the two circuits reflect the oscillation amplitudes across the two magnetic coils induced by the oscillators. The absorption of energy in the coil containing the solenoid plunger results in difference output values. These are compared in a comparator (ICI) and a high or low output determines whether a red (rt) or (gn) light emitting diode is on. In sophisticated systems, the output is fed into a status reporting and security control circuit via another transistor (T4).</p> |
