Security recognition monitoring circuitry for data transmission - evaluates frequencies and compares with threshold value for quality test

摘要

One of two frequencies has an associated digital 'one' and the other a 'zero' for demodulation, a filter separately recognises the frequencies to retrieve the digital data. At the outputs of the band-pass filters (BP1,BP2) detectors (D1,D2) select the two frequencies. Their outputs are fed to a differential amplifier (DV). The output of this produces the digital signal (DS) via a limiter. At the output of the differential amplifier (DV) a full-wave rectifier (G) is coupled. The dc. output voltage is compared with a predetermined thredhold The comparison may be digital or analog. USE - 2 FSK transmission.