Infrared alarm system

Claim 1

A security system connectable to a telephone line, the system comprising: a connector for connecting the system to the telephone line; a battery providing power to the system; a lens system for producing multiple detection ranges and radial detection zones; at least a first and second infrared sensor positioned behind said lens system providing substantially uniform detection through a field of view of 180 degrees and generating fluctuating sensor signals in response to external thermal sources crossing boundaries between said detection ranges or said radial detection zones within said field of view; an analog preamplifier electrically coupled to said first and second sensors for amplifying said sensor signals to generate amplified sensor signals; an alarm filter electrically coupled to said analog preamplifier and filtering said amplified sensor signals to generate filtered sensor signals; an analog to digital convertor electrically coupled to said alarm filter for converting said filtered sensor signals to generate digital sensor signals; memory for storing a plurality of stored signature values each containing a predetermined digital value corresponding to an authorized activity which should not trigger an alarm condition; a digital signal processor electrically coupled to said analog to digital convertor to provide real-time analysis said digital sensor signals, said digital signal processor providing digital filtering of said digital sensor signals to create high pass filtered signals, and storing said filtered signals in a signal buffer to create a time sequence of said filtered signals, calculating a continuous mean value of said stored filtered signals and determining a variance level between said running mean and said digital sensor signals, determining a coherence value between said digital sensor signals from said first infrared sensor and said second infrared sensor, and determining a similarity value between said digital sensor signals and each of said plurality of stored signature values, said digital signal processor generating a trigger to indicate the presence of an intruder if said variance level exceeds a predetermined variance level, said coherence value is below a predetermined coherence level, and each of said similarity value is below a predetermined similarity level for each of said plurality of stored signature values; an alarm, responsive to said trigger, to indicate the presence of an intruder; a DTMF tone generator electrically coupled to the telephone line through said connector to generate dual-tone multiple frequency (DTMF) tones to communicate status information about the security system, including said alarm indicating the presence of an intruder, to a remote location over the telephone line; a DTMF receiver electrically coupled to the telephone line through said connector to receive a sequence of tones over the telephone line; a DTMF filter electrically coupled to said receiver and analyzing each of said tones from said receiver to determine if one of said tones is a valid DTMF tones, said DTMF filter generating a detection signal within a specified period of time if one of said tones is the valid DTMF tone; a timer circuit continuously powered by said battery and generating periodic signals; a power manager, responsive to said periodic signals and said detection signal, to generate a control signal, said power manager ceasing generation of said control signal if said DTMF filter does not generate said detection signal within said specified period of time; a controller, responsive to said control signal, to selectively enable power to said receiver when said control signal is present and disable power to said receiver when said control signal is not present; a delay circuit to delay operation of said receiver circuit until said enabling power to said receiver is stabilized; a buffer electrically coupled to said receiver to store each of said valid DTMF tones received as digital data if said DTMF filter generates said detection signal; a security circuit preventing unauthorized access to said digital data in said buffer by requiring for access a predetermined DTMF access code sequence that is received by said receiver from the remote location over the telephone line; and a command circuit, responsive to said digital data, to process status request commands and digital signal processing commands received over the telephone line from the remote location if said predetermined DTMF access code sequence has been received by said receiver, whereby the security system provides real-time digital analysis of infrared sensor signals, a two direction DTMF communicator and reduced power consumption such that said battery will provide power to the securing system for at least one year.