The Master and Slave clock concept has been introduced to minimize the cost of the clocks and to distribute the clocks at all prominent places with master clock integration.
A slave clock is coordinated with a master clock. Slave clock coordination is usually achieved by the time signal received from the master clock. In the 19th and early 20th centuries, slave clocks were widely used throughout public buildings and business offices, and their remote operation was regulated by electrical signals sent by a centralized master clock.
These older styles of slave clocks either keep time by themselves, and are corrected by the master clock, or require impulses from the master clock to advance. Many slave clocks of these types remain in operation, most commonly in schools, power sector units built and handed over by over-seas companies.