Apparatus for discriminating between strain and magnetic stimuli in magnetic cored solenoid type transducer line sensors

Abstract

A dual signature perimeter detection system utilizing an elongated solenoid ype transducer having a ferromagnetic core as a line sensor is buried in the ground around an area to be protected against intrusion. One end of the transducer is impressed with constant frequency oscillator signals from a signal generator, while a resistance load impedance is connected across the other end of the transducer at the input side of an amplifier used to pass amplified signals selectively to the inputs of either a bandpass type filter or an A.M. detector, or to both simultaneously, then to their related alarms. The line sensor is sensitive to both magnetic and strain stimuli, but the system hereof, which utilizes dual alarm devices, not only provides for determining the type of stimulus creating the signals, but also improves the sensitivity and response uniformity of the transducer. Optimized oscillator frequency selection, transducer shielding, and subsequent filtering at the input to the electronics collectively minimize false alarms from otherwise potentially greater noise pick-up due to the system's use of an increased bandwidth.

Dependencies are inferred from the claim text.