Master/slave (technology)

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Master/slave is a model of communication where one device or process has unidirectional control over one or more other devices. In some systems a master is selected from a group of eligible devices, with the other devices acting in the role of slaves.[1][2][3]

In other words, "The master/slave configuration is basically used for load sharing purposes when two identical motors connected to two different drives are coupled to a common load".[citation needed] One drive is defined as the master and is configured for running in the speed-control mode whereas the other defined as slave is configured for running in torque-control mode.


  • In database replication, the master database is regarded as the authoritative source, and the slave databases are synchronized to it.
  • Hydraulic and pneumatic systems may use a master cylinder to control one or several slave cylinders.
  • Peripherals connected to a bus in a computer system.
  • Railway locomotives operating in multiple (for example: to pull loads too heavy for a single locomotive) can be referred to as a master/slave configuration - with the operation of all locomotives in the train slaved to the controls of the first locomotive. See - Multiple-unit train control.
  • Duplication is often done with several cassette tape or compact disc recorders linked together. Operating the controls on the master triggers the same commands on the slaves, so that recording is done in parallel.
  • In parallel ATA hard drive arrangements, the terms master and slave are used but neither drive has control over the other. The terms also do not indicate precedence of one drive over the other in most situations. "Master" is merely another term for device 0 and "slave" indicates device 1.
  • Rmpi[4] package in R is a standard master/slaves programming model.
  • On the Macintosh platform, rebooting into Target Disk Mode allows one computer to operate as a dumb disk enclosure presenting its storage devices to another via SCSI, FireWire, or Thunderbolt, essentially a slave mode bridge.
  • A master clock that provides time signals used to synchronize one or more slave clocks as part of a clock network.

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