Abstract: A PIR sensor apparatus and method make use of a dc amplifier circuit. The dc amplifier circuit amplifies a dc-coupled sensor signal generated by a PIR sensor for analysis. For improved accuracy, the dc amplifier circuit is controlled to compensate for dc offset in the sensor signal. In this manner, the dc amplifier circuit is capable of reducing false triggering and inhibited triggering due to excessive dc offset. The amplifier is dc-coupled to an output of the PIR sensor to receive the sensor signal. A detector detects a level of dc offset within the sensor signal. A controller controls the amplifier to compensate for the detected level of dc offset The amplifier may include a differential amplifier having a first input that receives the sensor signal and a second input that receives a reference voltage. A resistor-capacitor circuit can be provided to set the reference voltage received by the second input of the amplifier.

Abstract: In a wireless security system, the system controller includes one or more antennas for reception of signals from remote sensor-transmitter units. To detect antenna failure, the system controller generates a test signal with a known parameter and transmits this test signal via a first antenna. The system controller then measures the parameter of the corresponding test signal received, if any, via a second antenna, and compares the parameter of the corresponding test signal received to a predetermined threshold parameter. When the parameter of the test signal received via the second antenna differs from the threshold by a predetermined amount, or predetermined margin for error, an antenna failure message is generated.

Abstract: An apparatus and method for reducing errors in a battery powered sensing circuit uses two pull-up resistors. The first resistor has a value selected to minimize battery drain and the second resistor has a value selected to reduce dendrite or other parasitic parallel resistance. The resistors are selectively connected to the circuit based on a predetermined sequence and/or time interval.

Abstract: An active, relatively high gain, low power consuming band pass filter circuit centered at approximately 6 KHZ and having a pass band of 100-200 HZ. In a disclosed glass breakage sensor, the filter couples sensed ambient sounds of breaking glass to associated detection, driver and annunciator means. Signals of appropriate duration and frequencies indicative of breaking glass are thereby monitorable to define and induce an alarm condition within a security system.

Abstract: A short distance, battery powered, amplitude modulated, crystal controlled RF transmitter for transmitting encoded security information. In its preferred embodiments, the transmitter comprises a novel fifth overtone crystal oscillator which self-produces a carrier frequency at the third harmonic of the fifth overtone of the crystal's fundamental frequency, which carrier frequency is coupled by a series resonant trap, or a pi network, tuned to the carrier frequency to an amplifier stage where the carrier is amplitude modulated via pulse position encoded binary security data. In an alternative embodiment, the transmitter comprises matched crystal oscillator, tripler and amplifier stages. Also disclosed is an antenna including a battery clip contact.

Abstract: A method and apparatus in a security system whereby a central processing unit self learns the identities of its distributed wireless keypad and alarm transmitters. Each transmitter includes an electrically eraseable memory containing signal conditioning data and a pseudo randomly programmed identification code. During a transmitter initiating programming condition, the CPU captures the received identification code of each transmitter and establishes an identity code table by which subsequently received transmissions are confirmed as belonging to the system.

Abstract: A family of serially programmable integrated circuit transmitters for use in various sensor and user data input transmitters of a short-range radio frequency linked security system. Each transmitter transmits two bits of data for each data frame of a pulse position encoded message format with multiples of each message being transmitted with each transmission, the number of messages depending upon the type of message. Each user data input transmitter includes means for decoding keyboard entered data, re-circulating means for storing the user entered data and programmed system parameters and means for time partitioning intra and inter-message transmissions. Each sensor transmitter includes means for storing uniquely programmed system preconditioning parameters, means for sensing and verifying alarm conditions and means for time partitioning intra and inter-message transmissions.

Abstract: An automatic/remote instrument monitoring system and method are disclosed. RF transponder units are operatively connected to and monitor one or more parameters of a remotely located instrument. The transponders include RF receivers that sample received RF signals at a low duty cycle and look for a common wake-up signal transmitted from a mobile data collection unit. All transponders receiving the common wake-up signal simultaneously energize their respective transmitters and transmit their respective messages over a predetermined RF transmission bandwidth to receivers in the mobile unit. The time and frequency parameters of the transponder transmissions are varied in a manner such that the transmission signals of simultaneously transmitting transponders differ. A plurality of RF receivers in the mobile unit are respectively tuned to collectively receive the transponder transmissions, across the entire transmission bandwidth.