| 摘要 |
{PG,1 An intrusion detection unit comprises a compacitance having an {37 active{38 {0 field, the coupling of which is significantly increased when an intruder comes into conductive relation with a doorknob. The unit is hung on the inside doorknob and is so arranged that the doorknob is the transmitting element of the capacitor, while a separate plate is the receiving element of the capacitor. The capacitor field is maintained actively charged by a battery driven oscillator which operates at a substantially uniform frequency and amplitude. The intrusion detector circuit is complete in itself and is not externally grounded by the intruder. The signal receiving portion of the circuit incorporates a square law amplifier, and also has means for adjusting the reference level to which the signal is compared.
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