In telecommunication, a slave clock is a clock that is coordinated with a master clock. Slave clock coordination is usually achieved by phase-locking the slave clock signal to a signal received from the master clock. To adjust for the transit time of the signal from the master clock to the slave clock, the phase of the slave clock may be adjusted with respect to the signal from the master clock so that both clocks are in phase. Thus, the time markers of both clocks, at the output of the clocks, occur simultaneously.
In other areas, the term refers to satellite electrical clocks that operate remotely from an electrical pulse issued by a 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.
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Famous quotes containing the words slave and/or clock:
“It’s not the suffering of birth, death, love that the young reject, but the suffering of endless labor without dream, eating the spare bread in bitterness, being a slave without the security of a slave.”
—Meridel Le Sueur (b. 1900)
“The stars move still, time runs, the clock will strike,
The devil will come, and Faustus must be damned.
O I’ll leap up to my God: who pulls me down?
See, see, where Christ’s blood streams in the firmament.
One drop would save my soul, half a drop, ah my Christ.”
—Christopher Marlowe (1564–1593)