Patent ID: 7642910

Claim:
An alarm system receiver comprising: a. an antenna for sensing signals, b. a first filter for filtering said sensed signals at a first frequency to provide a first filtered signal and a second filter for filtering said sensed signals at a second frequency to provide a second filtered signal; c. a first local oscillator for providing first oscillator signals at said first frequency and a second local oscillator for providing second oscillator signals at said second frequency; d. a demodulator for inputting one of said first or second oscillator signals and a corresponding one of said first or second filtered signals to provide a demodulated signal; e. an interference detection circuit for determining if an interference signal is present in said demodulated signal and for providing an interference detection signal; f. a slicer circuit for generating a quantized demodulated signal from said demodulated signal, g. a microcomputer for processing said quantized demodulated signal as an alarm signal and for processing said interference detection signal to provide a frequency select signal; and h. analog switches for selecting, based on said frequency select signal, one of said first and second oscillator signals and one of said first and second filtered signals to be input into said demodulator.