A missing pulse detector is provided which has the capability of monitoring a varying frequency pulse source to detect the loss of a single pulse or total loss of signal from the source. A frequency-to-current converter is used to program the output pulse width of a variable period retriggerable one-shot...http://www.google.de/patents/US4142159?utm_source=gb-gplus-sharePatent US4142159 - Missing pulse detector for a variable frequency source
