Frequency selective calling receiver system - has filter for each frequency and logic timing for sequence identification

摘要

The frequency-selective-call receiver system consists of a demodulator with associated beat-frequency oscillator (M) (O), the output of which is connected to a number of filters - one for each different frequency used in the calling code (F1-4). Frequency bursts of about 60 ms intervals are used. - The amplified output of each filter passes to a flip-flop (K1-4). The output of the last switch in the series operates an indicator or alarm (AZ) when the corect sequence for that particular receiver is received. The out of the first flip-flop (K1) is connected to the second (K3) and also to a start circuit and gating units (AS)(OS). An AND-gate controls the final amplifier (V4).