A precise clock pulse from a central generator that may be used by multiple evices in many locations so that all work in step at the same speed. National timekeepers such as the National Bureaus of Standards in the US and the Greenwich Observatory in England are often the ultimate sources for these accurate timings for telephone, data, and satellite systems.

The clock usually found in the main office of a school or factory. For the most part, the only true "time-keeper" in a master-slave clock system. This guy sends out electrical impulses, on the minute or hour depending on the set up, advancing or correcting the clocks in classrooms and other areas of the buildings. Also rings the bells for class changes, etc.

A clock that keeps time for more than one clock dial

the cells that make up the suprachiasmatic nuclei (SCN) of the brain. This controls the overall circadian rhythm of the organism.

a floor standing unit

a resource that generates timing information