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:
“The man of genius, like a dog with a bone, or the slave who has swallowed a diamond, or a patient with the gravel, sits afar and retired, off the road, hangs out no sign of refreshment for man and beast, but says, by all possible hints and signs, I wish to be alone,—good-by,—fare-well. But the Landlord can afford to live without privacy.”
—Henry David Thoreau (1817–1862)
““Pop” Wyman ruled here with a firm but gentle hand; no drunken man was ever served at the bar; no married man was allowed to play at the tables; across the face of the large clock was written “Please Don’t Swear,” and over the orchestra appeared the gentle admonition, “Don’t Shoot the Pianist—He’s Doing His Damndest.””
—Administration in the State of Colo, U.S. public relief program. Colorado: A Guide to the Highest State (The WPA Guide to Colorado)