Auxiliary timing source for ac-powered electronic clocks
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United States of America Patent
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Jan 6, 1987
Grant Date -
N/A
app pub date -
Apr 17, 1985
filing date -
Apr 17, 1985
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
An apparatus and method that provides an auxiliary timing source for electronic clocks, normally powered by alternating current (ac). The apparatus and method includes calibrating an inexpensive resistor-capacitor oscillator, powered by a battery. The oscillator is calibrated during normal ac operation by comparing a digital timing pulse derived from the oscillator and a digital timing pulse derived from the alternating current. When a power failure occurs, the calibrated oscillator provides an inexpensive and accurate auxiliary timing source. The apparatus and method may also include a non-volatile solid-state storage medium for storing the time of day and a set of timing instructions in the event that the battery becomes drained.
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