Simplex Communication - ITU-T Definition: One Way Signaling at A Time

ITU-T Definition: One Way Signaling at A Time

According to the ITU-T definition, a simplex circuit is one where signals can flow in only one direction at a time. At other times communications can flow in the reverse direction. A more common term for this application is half-duplex. Examples are intercoms, and two way radios such as walkie-talkies, citizens band, and mobile radios used dispatch police, firefighters, and taxicabs.

The old Western Union company used the term simplex when describing the half-duplex and simplex capacity of their new transatlantic telegraph cable completed between Newfoundland and the Azores in 1928. The same definition for a simplex radio channel was used by the National Fire Protection Association in 2002.