Abstract: A self-powering input buffer includes a first circuit leg that stores a charge, such as in a capacitor and a second circuit leg with a buffer powered by the first circuit leg that detects a state of an input with reference to a threshold. A transistor switch is coupled between the circuit legs. If the buffer detects an input voltage higher than the predetermined threshold the buffer drives the transistor switch ON to conduct current from the first circuit leg to the output. If the buffer detects an input voltage lower than the predetermined threshold the buffer drives the transistor switch OFF to disconnect the first circuit leg from the output. During a voltage dip the capacitor provides supplemental power as long as the input is above the threshold.

Abstract: A missing pulse detector is disclosed in which the absence of a pulse in a variable frequency periodic pulse train is detected and distinguished from a reduction in the pulse repetition rate. Between successive pulse train pulses a first counter counts clock pulses at a first rate and develops a maximum count related to the time duration between successive pulses. This maximum count is maintained by a latch circuit during the next time duration between successive pulses and is compared with the count of a second pulse counter which counts clock pulses during successive pulse train pulses at a second rate normally less than the first incrementing rate. When the count of the second counter exceeds by a predetermined amount the latched count of the first counter, this indicates the occurrence of longer time duration and a count comparator and logic circuit provides an arming output signal.