Master clocks are widely used in hospitals.
 

Master clocks are widely used in hospitals, schools, railway networks, post offices and telephone exchanges. As a part of a clock network the master clock provides the timing signals to synchronize the slave clocks.

In large offices or factories where they need to work on the same time, a central clock was used and this central clock sent the time to various small clocks or slave clocks throughout the office or factory. In olden days master clocks were electrically maintained pendulum clocks. The clock timing signals were electrical pulses which were fed to the equipment through pairs of wires. They were housed in wooden cases with a glass front and the dial was mounted in the top and looked much like a conventional clock.

But today there are wireless master clocks that can be installed easily and are also cheaper than the electrical master clocks. These master clocks are free of running wires and they are more reliable and inexpensive. They get their time from the internet and have few moving parts. They can be installed in minutes whereas the old master clocks took days to get installed. They do not require special cables, they need a standard CAT 5 cable.

Some of these master clocks do not need electric connection they need just an Ethernet connection and are run by power over Ethernet (POE). A few of these clocks use transmitters with a quarter to half mile range. Technology has developed so much that some clocks do not need  clock transmitters, a network connection and a web connection will do for the master clock system to work.

The master clocks have digital displays or the normal clock faces. They help in uniform time keeping in large factories and schools and hospitals.