Abstract: The frequency-modulated demodulator is provided in which the frequency-modulated signal as having a relatively narrow range of frequency modulation is demodulated by providing a pulse which corresponds to the positive half-wave cycles of the signal and then generating an extended duration pulse from the initiation of the first pulse produced to the second pulse produced in two consecutive cycles. In this manner every other cycle of the FM demodulated signal provides an output pulse which substantially corresponds to the duration of one cycle of the FM signal. A high frequency clock on the order of 1,000 times faster than the frequency of the extended duration signals is gated through for substantially the entire width of the extended pulse duration. The number of clock pulses that are gated through or counted to provide an indication of the frequency signal, a sampled basis corresponding to every other cycle of the FM signal.

Abstract: A semiconductor circuit for protecting battery powered electronic devices from damage due to polarity reversal. A metal oxide semiconductor is employed in series with the power source to switch the power input as appropriate. A first embodiment simply disables the power source input upon improper polarity. A second embodiment actually reverses the effective polarity to the load. Because the source-to-drain impedance of the metal oxide semiconductor device is resistive, a number of protection devices may be used in parallel to achieve an arbitrarily low voltage drop between power source and load for a given current drain.