Abstract: A circuit arrangement, suitable for a burglar security device, has coincidence operation of two Doppler alarm devices. The difference frequency signal of the two Doppler frequency signals which are produced by the movement of an object within a protected area is employed as an alarm-triggering signal. The circuit arrangement has a product detector for the formation of the difference frequency signals, a subsequently connected low pass filter and a threshold value detector. The threshold value detector is designed such that the amplitude value of its detection threshold can be changed in dependence upon the frequency of a control signal supplied thereto, the frequency of the control signal being derived from one of the Doppler frequency signals, the dependence being designed such that the frequency dependence of the amplitude value of the detection threshold is fundamentally equal to the frequency-dependent attenuation characteristics of the low pass filter.

Abstract: The reflected signal of a microwave or ultrasonic Doppler intrusion detector is split into two different channels, each containing a mixer for hetrodyning the received signal with a reference signal. The reference signal for one mixer is the transmitted signal, while the reference signal for the other mixer is the transmitted signal with a phase shift. Thus the outputs of the mixers are of the same frequency but different phase. A phase comparator produces two mutually exclusive pulse trains as a function of the outputs of the two mixers, one said output representing motion toward the detector and the other representing motion away from the detector. These pulse trains are applied through a bidirectional counter to upper and lower limit sensors. An alarm circuit is activated if either limit is exceeded, thus providing an alarm in response to sufficient motion in either direction.

Abstract: An alarm or signalling system between a transmitter station and a receiver station either or both of which may be in motion. A signal is selectively radiated from the transmitter station for detection at the receiver station. The receiver station includes processing means for responding to the received signal and producing a new signal indicative of selected physical relationships between the transmitter and receiver stations during the period of signal transmission and reception. The modified signal may indicate approaching or departing relative motion and/or magnitude of separation. One embodiment may incorporate synchronizing signals transmitted from a central control station. This embodiment may include receiver stations with and without the synchronizing equipment.

Abstract: A microwave radar type of intruder detection system incorporating signal sensing, storing and comparison logic which enables the system to self-adapt to any preselected environment and produce a signal in the event of a predetermined change from the ambient conditions of the preselected environment.

Abstract: A microwave movement detector which is capable of discriminating between progressive or unidirectional movement such as that by an unauthorized intruder and reciprocating movement such as by a curtain. The detector includes a pair of receiver/mixer diodes into which a transmitted signal is mixed with a surveying signal causing a phase difference so that the resultant signals have a different phase relationship amplifying the resultant signals feeding the signal into an integrating circuit in similar counter so that an alarm is sounded when the counter reaches a high or low threshold level.

Abstract: An electronic detection system for detecting intruders employs a transmission line as a sensing element. The transmission line is positioned about the perimeter of the area to be protected. An antenna applies pulsed RF energy to the line. An intruder in the field of the line causes an RF reflection back toward the source, which reflection may be detected by Doppler range-gating techniques.

Abstract: A receiver in which the detection sensitivity of a detection diode is adjustable as a function of the polarization current, and is controlled by means of a feedback circuit provided with a delay element so that changes in the received signals having a frequency below a value determined by the delay element are eliminated.

Abstract: An electrical or supersonic wave having a predetermined frequency is emitted as a monitor wave from an emitting device into a zone to be monitored. When a moving object having an inherent velocity range intrudes into the zone, a reflected wave of the monitor wave from the moving object is received by a receiver and an alarm signal is issued when the frequency deviation of the reflected wave relative to the frequency of the emitted monitor wave is within the frequency range corresponding to the velocity range. The alarm device has a circuit for producing a first alarm responsive to the alarm signal, a circuit for changing the frequency of the monitor wave when the first alarm is issued, and a circuit for producing a second alarm when a further alarm signal is obtained from the monitor wave with changed frequency within a predetermined time after change of the monitor wave frequency.

Abstract: An intrusion alarm of the kind in which a radiation field is transmitted in an area to be supervised; the reflected field is received and compared with the transmitted field, and a comparison signal is produced the frequency of which is indicative of the speed of movement of an object in the supervised area. A signal processor receives the comparison signal and generates an alarm if the comparison signal contains components in a selected frequency range. The processor includes a unique filter block which removes unwanted frequency components outside the range. The filter block includes a pulse generator which generates a constant amplitude pulse train, each pulse corresponding to a pulsation of the comparison signal, and control elements which control the duty cycle of the pulse train so that as the frequency of the comparison signal increases, the average level of the pulse train first increases and then decreases.

Abstract: Microwave apparatus for detecting the movement of a moving object comprising a Gunn oscillator device having input terminals that are capable of receiving a potential difference which serves to produce a bias current in the device, said potential difference being subject to variations, the device being responsive to a constant potential difference and operative to radiate microwave energy at a first frequency, and further responding to Doppler shifted energy reflected from the moving object and producing a variation in the bias current, an operational amplifier responsive to the potential difference and a reference signal for developing a first signal when the potential difference exceeds the reference signal and a second signal when it is less, a series-pass transistor connected to a source of DC potential and the operational amplifier and being switchable between a conducting and a non-conducting state in response to the first and second signals and serving to maintain the potential difference at a constant

Abstract: An ultrasonic or microwave intrusion detection system uses a transmitter having one or more transducers or antennas for maintaining wave fields in the area to be protected and fed by one or more transducers or antennas which detects echo reflections of the energy from within the area. The receiver employs two mixers energized to be mixed with the echo signals and a portion of the energy from the transmitter, one of the mixers receiving such transmitter energy with 90.degree. phase shift relative to the other mixer. The outputs of the two mixers thus are in quadrature phase relative to each other and define a rotating vector which contains the information relating to the echo signals. The product of these quadrature signals obtained by multiplying them together is processed continuously to obtain target information in the presence of substantially larger clutter return signals and other interference.