Smart clock: a new time

The smart clock provides for the automatic synchronization of any clock to an external standard with a minimum of measurements. The concept covers a range of applications from wrist watches and household clocks to high accuracy clocks. The smart clock enhances the accuracy or stability of a clock or oscillator by comparing it with an external standard. The smart clock algorithm uses optimal estimation and prediction to apply a correction to the output of the oscillator, maintaining any combination of time or frequency accuracy or stability within specified limits. The algorithm decides when external measurements are necessary to maintain the desired accuracy or stability. A tutorial description of the smart clock system is presented, together with an example of how it could be used to maintain a simple clock to 1 s using measurements over telephone lines