Editing Diplexer (section)

==Common uses==
A diplexer allows two different devices to share a common communications channel. Typically, the channel is a long coaxial cable, and a diplexer is often used at both ends of the coaxial cable. The plan is feasible if the two devices operate on different frequencies.  The plan is economical if the diplexers cost less than running a second cable.

Diplexers are typically used with radio receivers or transmitters on different, widely separated, frequency bands.  A single city radio tower might have a police department antenna on 460&nbsp;MHz and a fire department antenna on 156&nbsp;MHz.  A diplexer at the top combines the two antenna signals to the single coaxial feedline, and a second identical diplexer inside the building separates the feedline signals to the two dispatch radios. Some diplexers support as many as four antennas or radios that work on different radio bands.

Diplexers are also commonly used where a multi-band antenna is used on a tower, with a common feedline. The diplexer will split the two bands inside the building (such as VHF and UHF systems combined with a diplexer onto a common antenna).