Editing Master–slave (technology) (section)

== Examples ==
{{More citations needed|section|date=November 2022}}
In photography, [[Flash synchronization#Wireless sync|secondary]], or slave, flash units are connected to a master unit to provide synchronized lighting.

Parallel audio duplication often entails multiple [[Sound recording and reproduction|recording]] with linkdevices (i.e. for [[cassette tape]] or [[compact disc]]) linked together so that operating the controls of a master device triggers the same commands on slave devices.

Railway [[locomotive]]s operating in the same train (for example, to pull a load too heavy for a single locomotive) may be configured for master–slave operation with all but one of the locomotives controlled from the first. See [[Multiple-unit train control]].

In a [[hydraulic]] system, a [[master cylinder]] is a control device that converts [[force]] into hydraulic pressure that drives movement in a slave cylinder at the other end of the hydraulic line. A common application is a vehicle [[brake]] system.

A [[master clock]] provides [[time signal]]s used to synchronize one or more [[slave clock]]s as part of a [[clock network]];<ref name="USNO">{{Cite web |title=USNO Master Clock |url=http://www.usno.navy.mil/USNO/time/master-clock |archive-url=https://web.archive.org/web/20100310143915/http://www.usno.navy.mil/USNO/time/master-clock |archive-date=2010-03-10 |access-date=2009-10-07}}</ref> a slave clock receives and displays the time from a master; though it may be able to keep time itself if the master is not working.

=== Computing ===
[[Bus (computing)|Computer bus]] protocols often use a master-slave relationship. For instance, a [[USB]] host manages access to the USB bus shared by any number of USB devices. A [[serial peripheral interface]] (SPI) bus typically has a single master controlling multiple slaves.<ref name=":0">{{Cite web |last=Dhaker |first=Piyu |date=2018 |title=Introduction to SPI Interface |url=https://www.analog.com/en/analog-dialogue/articles/introduction-to-spi-interface.html |url-status=live |archive-url=https://web.archive.org/web/20230525152752/https://www.analog.com/en/analog-dialogue/articles/introduction-to-spi-interface.html |archive-date=2023-05-25 |access-date=2023-07-21 |website=[[Analog Dialogue]]}}</ref><ref>
[[Open Source Hardware Association]].
[https://www.oshwa.org/a-resolution-to-redefine-spi-signal-names/ "A Resolution to Redefine SPI Signal Names"].
</ref><ref>
Nathan Seidle.
[https://www.sparkfun.com/spi_signal_names "A redefinition of SPI signal names"].
</ref><ref>
Utah State University ECE 3700
[https://left.engr.usu.edu/courses/3700/assignments/2_rtl/2_communication/1_SPI_READ/assigned_tasks.html "SPI Chip-to-Chip Communication"]
</ref> [[I2C]] and [[I3C (bus)|I3C]] may even have multiple masters on a bus. [[Modbus]] also uses a master device to initiate connection requests to slave devices.

An edge-triggered [[Flip-flop (electronics)|flip-flop]] can be created by arranging two [[Flip-flop (electronics)#Gated latches|gated latches]] in a master–slave configuration. It is so named because the master latch controls the slave latch's value and forces the slave latch to hold its value, as the slave latch always copies its new value from the master latch.

In [[database replication]], the master database is the authoritative source. The slave or replica database is controlled by the master database which repeats its update commands (for example by way of [[event log]]) to the slave.  The slave therefore retains an exact copy of transaction processed by the source database (up to the most recently transmitted log)<ref>{{cite web |title=MySQL Master-Slave Replication: 6 Easy Steps {{!}} Airbyte |url=https://airbyte.com/data-engineering-resources/master-slave-replication |website=airbyte.com |language=en |quote=The binary logs containing the changes are shipped from the master server to the slave servers so that they can exactly mimic what the main server is doing}}</ref> This scheme is not as strict as electronic devices sharing a clock, however the slave database only does what the master tells it, unless the slave is promoted due to failure of the master.  Some databases implement so called "[[multi-master replication]]", where a mix of writeable master nodes and readable nodes are used.  These databases are used in scenarios where performance is an acceptable tradeoff for [[ACID]] properties, for example non mission critical data, like suggesting similar purchases.