Abstract: An intrusion alarm system has a number of satellites each connected to a master by an unshielded cable having only four conductors, namely two power conductors, a drive signal conductor which supplies drive to the satellite transmitter and the satellite control circuit, and an alarm conductor. When an intrusion is detected by a satellite, its control circuit transmits a high level alarm signal on the alarm conductor to the master and also sets a latch in the satellite. The master has a rocker switch which an investigator turns off when he arrives at the supervised premises. This turns off the drive signal to the satellite and causes a counter in the master to send a set of interrupting counting pulses to the satellites on the drive conductor. Each satellite has a counter which counts the pulses if that satellite's latch has been set and sends a pulse back to the master on the alarm conductor immediately after the count associated with that counter.

Abstract: An intrusion alarm system has a number of satellites each connected to a master by an unshielded cable having only four conductors, namely two power conductors, a drive signal conductor which supplies drive to the satellite transmitter and the satellite control circuit, and an alarm conductor. When an intrusion is detected by a satellite, its control circuit transmits a high level alarm signal on the alarm conductor to the master and also enables, but does not operate, a speaker in the satellite. The master has a rocker switch which an investigator turns off when he arrives at the supervised premises. This turns off the drive signal to the satellite. The control circuit of the satellite that caused the alarm responds by sounding its speaker, enabling determination of where the alarm occurred.

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: An intrusion alarm system has a number of satellites each connected to a master by an unshielded cable having only four conductors, namely two power conductors, a drive signal conductor which supplies drive to the satellite transmitter and the satellite control circuit, and an alarm conductor. When an intrusion is detected by a satellite, its control circuit transmits a high level alarm signal on the alarm conductor to the master and also enables (but does not operate) a speaker in the satellite. The master has a rocker switch which an investigator turns off when he arrives at the supervised premises. This turns off the drive signal to the satellite. The control circuit of the satellite that caused the alarm responds by sounding its speaker, enabling determination of where the alarm occurred.