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 Museum is not meant either for the wanderer to see by accident or for the pilgrim to see with awe. It is meant for the mere slave of a routine of self-education to stuff himself with every sort of incongruous intellectual food in one indigestible meal.”
—Gilbert Keith Chesterton (1874–1936)
“Whoever considers morality the main objective of human existence, seems to me like a person who defines the purpose of a clock as not going wrong. The first objective for a clock, is, however, that it does run; not going wrong is an additional regulative function. If not a watch’s greatest accomplishment were not going wrong, unwound watches might be the best.”
—Franz Grillparzer (1791–1872)