In which device multiplexer is used?

Can you elaborate on the specific context in which a multiplexer is used in a device? Multiplexers, or muxes, are commonly employed in various electronic systems and devices to efficiently manage multiple input signals and select one or more to be transmitted through a single output channel. They can be found in applications ranging from communication systems to data processing units. Could you please specify whether you're referring to a particular type of device, such as a computer, network router, or any other electronic equipment, and what specific role the multiplexer plays within that device? Understanding the context will help me provide a more accurate and relevant description.