Abstract: An AM/FM receiver which demodulates radio signals by computing estimates of spectral parameters of the radio signals. Three spectral parameter estimation circuits are selectively formed from a number of shared circuits according to the type of modulation of the radio signal. In the case of frequency modulated signals, the respective strengths of the desired signal and interfering signals dictate the most favorable circuit configuration. The first estimation circuit calculates the instantaneous amplitude of the radio signal which corresponds to the modulating audio signal of an AM signal, the second estimation circuit calculates the instantaneous frequency of the radio signal which corresponds to the modulating audio signal of an FM signal, and the third estimation circuit calculates the power mean frequency of the radio signal which, when calculated over a short period of time relative to the rate of change of the FM signal, also corresponds to the modulating audio signal.

Abstract: A reliable pulse source circuit utilizing two independent but synchronized pulse generators is disclosed. The pulse source circuit maintains output pulses even though one pulse generator fails regardless of the failure mode, i.e., whether the output of the failed generator is stuck high or stuck low. A toggle flip-flop responsive to the presence and absence of pulses from the two generators and its own state outputs controls gating circuitry to generate a sequence of output pulses wherein alternate output pulses occur in response to pulses of one generator and the remaining output pulses occur in response to pulses of the other generator, and if either generator fails, all output pulses occur in response to the pulses of the other generator.

Abstract: A tone detector circuit for detecting the presence of a certain tone or tones in an input signal. An estimate is calculated for each of the following three parameters of the band limited spectrum of the input signal: total power, power mean frequency, and mean square power bandwidth. Each of the three input spectrum parameters is compared to the same parameter of the tone or tones desired to be detected. If a match within certain bounds occurs on all three parameters, the desired signal has been detected.