A
master clock is a precision
clock that provides timing signals to synchronise
slave clocks as part of a
clock network. Networks of electric clocks connected by wires to a precision master pendulum clock began to be used in institutions like factories, offices, and schools around 1900. Today many
radio clocks are synchronised by radio signals or internet connections to a worldwide time system called
Coordinated Universal Time (UTC) which is governed by master
atomic clocks in many countries.