Blackberry updating time zones 98 stuck
The present invention is therefore intended to provide a relatively low cost, easily installed and aligned clock which is capable of receiving UTC time signals on any one of three frequencies, displaying the time to an accuracy of ±10 milliseconds, and regularly and continuously updating the timing of a microprocessor used to control the clock.
The present invention is not subject to the timing inaccuracies inherent in a temperature-stabilized crystal oscillator circuit nor does it exhibit the cumulative time error inherent in atomic clocks.
The mean sidereal day is 23 hours, 56 minutes, and 4.09 seconds.
Because of variations in the rotational speed of the earth, sidereal time is not perfectly uniform.
A 100 Hz subcarrier contains binary coded decimal (BCD) signals that supply day-of-the-year, hour and minute information.This time scale is based upon the mean time of rotation of the earth about its axis in relation to the vernal-equinox point in the sky.It is determined by observing the meridian transits of stars.A time difference correction is provided to a digital-to-analog converter which provides an appropriate voltage to a varactor diode in a crystal oscillator circuit for adjusting the microprocessor's operating frequency until it can no longer resolve a difference between the received RF timing signals and its internal timer.This permits highly accurate clock operation in between the periodic reference time updates and eliminates cumulative time error.