| 摘要 |
<p>1280072 Proximity switching systems WAGNER ELECTRIC CORP 20 March 1970 [16 April 1969] 13470/70 Heading G1N [Also in Division G4] In a capacitive proximity sensor, a relaxation oscillator 34 is supplied with a D.C. voltage derived by stepping up the output of a batterydriven oscillator 14, the output of the relaxation oscillator 34 being a function of the capacitance of an antenna 44, said output being amplified at 48, 60 and use to operate an alarm or indicator 81. As described, the oscillator 14 provides a series of pulses each including a plurality of high frequency alternations which are rectified at 28 so as to provide power for a relaxation oscillator 34. If a person moves into proximity with antenna 44, the output of oscillator 34 increases, the resulting voltage being amplified by transistor 48 and rectified by voltage doubler 54, 56, the resulting voltage being amplified at 60 and used to turn on a trigger circuit 70, 72 which operates a relay 76 so as to set off an alarm 81. The alarm is re-set by contacts 84. Part of the output of oscillator 14 is rectified at 86 and used as bias for the trigger circuit 70, 72. In Fig.2 (not shown) resistor 46 is replaced by a series-parallel switched arrangement of resistors so as to control the sensitivity of the system. In Fig.4 (not shown) transistors 70, 72 are replaced by a single transistor, the relay having a hold-in contact.</p> |
