Katana VentraIP

Duplex (telecommunications)

A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow for simultaneous communication in both directions between two connected parties or to provide a reverse path for the monitoring and remote adjustment of equipment in the field. There are two types of duplex communication systems: full-duplex (FDX) and half-duplex (HDX).

In a full-duplex system, both parties can communicate with each other simultaneously. An example of a full-duplex device is plain old telephone service; the parties at both ends of a call can speak and be heard by the other party simultaneously. The earphone reproduces the speech of the remote party as the microphone transmits the speech of the local party. There is a two-way communication channel between them, or more strictly speaking, there are two communication channels between them.


In a half-duplex or semiduplex system, both parties can communicate with each other, but not simultaneously; the communication is one direction at a time. An example of a half-duplex device is a walkie-talkie, a two-way radio that has a push-to-talk button. When the local user wants to speak to the remote person, they push this button, which turns on the transmitter and turns off the receiver, preventing them from hearing the remote person while talking. To listen to the remote person, they release the button, which turns on the receiver and turns off the transmitter. This terminology is not completely standardized, and some sources define this mode as simplex.[1][2]


Systems that do not need duplex capability may instead use simplex communication, in which one device transmits and the others can only listen. Examples are broadcast radio and television, garage door openers, baby monitors, wireless microphones, and surveillance cameras. In these devices, the communication is only in one direction.

for data communications on 3G mobile networks

UMTS-TDD

for data communications on 4G mobile networks

LTE-TDD

wireless telephony

DECT

Half-duplex networks based on carrier-sense multiple access, for example 2-wire or hubbed Ethernet, Wireless local area networks and Bluetooth, can be considered as time-division duplexing systems, albeit not TDMA with fixed frame-lengths.

packet switched

WiMAX

PACTOR

ISDN BRI , variants using the time-compression multiplex (TCM) line system

U interface

a digital subscriber line (DSL) standard developed by the ITU-T

G.fast

(2003). Computer Networks. Prentice Hall. ISBN 0-13-038488-7.

Tanenbaum, Andrew S.