GB1386223A - Ultrasonic microwave doppler intrusion alarm system - Google Patents

Abstract

1386223 Intruder alarms E-SYSTEMS Inc 30 May 1973 [20 July 1972] 25711/73 Heading G4N [Also in Division H4] An intruder alarm system comprises ultra-. sonic and microwave movement detection units, an integrator and signal level detector coupled to the microwave unit, a test circuit responsive to fault conditions, and means for providing an alarm signal when movement indication signals co-exist at the unit outputs. A central housing (10) (Fig. 1, not shown) contains a microwave transmit/receive antenna (20) and utrasonic receiver elements (18), outboard housings (12), (14) containing ultrasonic transmitting elements (22). In Fig. 2 the ultrasonic 30 and microwave system 32 are connected to logic 34, which gives the alarm signal when system 30, 32 gives simultaneous outputs. A line 38 from a central controller (24) (Fig. 1, not shown) applies selftest signals to the systems to continuously monitor their operation. Signals are also provided by the systems to indicate if the ultrasonic and microwave oscillators are working, and these signals are passed to logic 40. Fig. 3 (not shown) illustrates the microwave system in detail. The doppler movement signal, if present, is rectified and integrated and, if above a certain level, passed to logic 34. An attenuator 50 injects a test signal from line 38 into the pre-amplifier 48, the signal simulating a moving intruder. A signal from mixer 44, fed to logic 40 of Fig. 2, indicates if oscillator 46 is operative. Fig. 6 illustrates the ultrasonic system. Outboard units 108, 114 contain the ultrasonic transmitting elements 22, and central unit 104 contains receiving elements 18. The doppler signal from mixer 120 is filtered and amplified at 122 and then rectified, integrated and level detected as in the microwave receiver. The signal is then passed to logic 34. The test input from the controller unit is a square wave provided on line 130. This pulses a modulator 128 which gives bursts of signals within the doppler passband. The test bursts are then applied to filter-amplifier 106 and the system function therefore checked. Signals are also provided from units 108 and 114 to a unit 112 which both monitors the units 108, 114 for correct functioning and also supplies them with ultrasonic power from oscillator 128. Signals on lines 166, 158 will indicate tampering with units 108, 114 respectively, e.g. disconnection of them from the ultrasonic power supply, shorting of the unit connections or a failure of oscillator 118. Oscillator 118 may be arranged to give a frequency changing with temperature in the same way as the transmitter transducer resonant frequency changes to always ensure maximum power output. Detailed circuits of the microwave oscillator 46, units 108, 114, oscillator 118 and modulator 128 are given. Reference has been directed by the Comptroller to Specification 964,752.