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:
“Chippenhook was the home of Judge Theophilus Harrington, known for his trenchant reply to an irate slave-owner in a runaway slave case. Judge Harrington declared that the owner’s claim to the slave was defective. The owner indignantly demanded to know what was lacking in his legally sound claim. The Judge exploded, ‘A bill of sale, sir, from God Almighty!’”
—For the State of Vermont, U.S. public relief program (1935-1943)
“What says the Clock in the Great Clock Tower?
And all alone comes riding there
The King that could make his people stare,
Because he had feathers instead of hair.
A slow low note and an iron bell.”
—William Butler Yeats (1865–1939)