Abstract: The invention provides an alarm panel connected to a telephone line. The alarm panel comprises a microprocessor connected to a circuit which operates in two states: passive and active. In the passive state, the alarm panel monitors the line for a ring signal and tests the integrity of the telephone line. In the active state, the alarm panel seizes the telephone line and provides full bi-directional communication with a receiver through the telephone line. The circuit is designed such that the individual subcircuits for each state operate independently of each other and can be modified to meet various regulatory requirements without affecting the other circuits. The circuit draws low current in the passive state. Finally, the circuit is separated from the microprocessor using only 2 or 3 optocouplers.

Abstract: An arrangement and method for processing signals from infrared microwave and/or ultrasonic intrusion detectors is disclosed which allows the signal to be processed at different amplitude levels to recognize different signal characteristics. This capability to analyse the signal at different values allows further customizing of the system for particular applications and provides information useful in recognizing and dealing with unwanted signal changes typical of the environment which can affect the reliability of the alarm criteria and/or trouble condition criteria. An assessment of the environment in a preferred aspect allows customizing of the alarm criteria to take into account the operating environment of the particular sensor or sensors. The system also accommodates increasing the effect on certain portions of the signal when considering the net overall effect of the signal.