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US 5,416,435 AGranted
Time measurement system
AssigneeNokia Mobile Phones Ltd.
InventorsHarri Jokinen, Sakari Jorri
Life of this patent
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Abstract
A time measurement system for measuring time accurately with an inaccurate clock, in which two clock oscillators are compared and the momentary error of the slower clock oscillator is measured. When the error change rate of the slower clock oscillator is slow enough the fast clock oscillator can be switched off for longer time intervals. With the help of this apparatus and method of operation power can be saved in portable equipment which requires accurate time measurement.
Claims9
An apparatus for producing pulses comprising;
- i) a first signal source for outputting a relatively high frequency signal (f.sub.1) and a second signal source for outputting a relatively low frequency signal (f.sub.2);
- ii) an error calibrating means for measuring a frequency deviation of said relatively low frequency signal (f.sub.2) by periodically comparing said relatively low frequency signal (f.sub.2) with said relatively high frequency signal (f.sub.1);
- and
- iii) control means for selectively coupling said relatively high frequency signal (f.sub.1) and said relatively low frequency signal (f.sub.2) as inputs to a counter means to control outputting of said pulses, said control means (6) coupling said relatively high frequency signal to said counter means for a time period dependent upon a deviation of said relatively low frequency signal (f.sub.2) from said relatively high frequency signal (f.sub.1) as determined by said error calibrating means.
1 more element
Dependencies are inferred from the claim text.