A multiplexer (mux) is a device that takes multiple video sources and allows them to be viewed on one monitor. Typically they come in four, nine, and 16 position units. By using a multiplexer the need for multiple monitors is eliminated as the mux is capable of displaying multiple camera shots onto one monitor.

The multiplexer is typically connected to a VCR for archiving, nowadays the DVR will accomplish the viewing and recording functions and the Mux has been relegated for use when more than 4 pictures need to be displayed on one screen. If your having trouble selecting the right multiplexer for you, then please visit the CCTVhelp.com forum for support