Duplex (telecommunications)

half-duplexfull-duplexduplexfull duplexFDDbidirectionalduplexingtime division duplexbi-directionalfrequency-division duplex
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.wikipedia
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Telephone

phonetelephonesLocal Telephone Service
An example of a full-duplex device is a telephone; the parties at both ends of a call can speak and be heard by the other party simultaneously.
Telephones are duplex devices, meaning they permit transmission in both directions simultaneously.

Walkie-talkie

walkie talkiewalkie-talkiesradio
An example of a half-duplex device is a walkie-talkie 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 but turns off the receiver, so they cannot hear the remote person.
A walkie-talkie is a half-duplex communication device.

Simplex communication

simplexunidirectionalCDS-link receiver
Systems that do not need the duplex capability may instead use simplex communication, in which one device transmits and the others can only "listen".
A duplex communication channel requires two simplex channels operating in opposite directions.

Channel access method

multiple accesschannel accessmultiple access method
Where channel access methods are used in point-to-multipoint networks (such as cellular networks) for dividing forward and reverse communication channels on the same physical communications medium, they are known as duplexing methods.
Examples of shared physical media are wireless networks, bus networks, ring networks and point-to-point links operating in half-duplex mode.

Communications system

communication systemcommunication systemstelecommunications system
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.
A duplex communication system is a system composed of two connected parties or devices which can communicate with one another in both directions.

Point-to-point (telecommunications)

point-to-pointpoint to pointpoint-to-point connections
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.
A switch on the other hand provides a series of point-to-point circuits, via microsegmentation, which allows each client node to have a dedicated circuit and the added advantage of having full-duplex connections.

LTE (telecommunication)

LTE4G LTE3GPP Long Term Evolution
The Chinese TD-LTE 4-G, TD-SCDMA 3-G mobile communications air interface.
LTE supports scalable carrier bandwidths, from 1.4 MHz to 20 MHz and supports both frequency division duplexing (FDD) and time-division duplexing (TDD).

Ethernet

wiredJabbernetworking
Full-duplex Ethernet connections work by making simultaneous use of two physical twisted pairs inside the same jacket, which are directly connected to each networked device: one pair is for receiving packets, while the other pair is for sending packets.
Furthermore, the 10BASE-T standard introduced a full duplex mode of operation which became common with Fast Ethernet and the de facto standard with Gigabit Ethernet.

G.fast

XG-fast
G.fast, a digital subscriber line (DSL) standard developed by the ITU-T
G.fast uses time-division duplexing (TDD), as opposed to ADSL2 and VDSL2, which use frequency-division duplexing.

Radio receiver

receiverreceiversRadios
Frequency-division duplexing (FDD) means that the transmitter and receiver operate at different carrier frequencies.
Two-way voice communications - A two-way radio is an audio transceiver, a receiver and transmitter in the same device, used for bidirectional person-to-person voice communication. The radio link may be half-duplex, using a single radio channel in which only one radio can transmit at a time. so different users take turns talking, pressing a push to talk button on their radio which switches on the transmitter. Or the radio link may be full duplex, a bidirectional link using two radio channels so both people can talk at the same time, as in a cell phone.

Digital Enhanced Cordless Telecommunications

DECT DECTDECT Forum
DECT wireless telephony
DECT uses time division duplex (TDD), which means that down- and uplink use the same frequency but different time slots.

U interface

UU k0 U K0 -Interface
ISDN BRI U interface, variants using the time-compression multiplex (TCM) line system
To that end, ITU-T recommendation G.961 specifies two duplex transmission technologies for the ISDN U interface, either of which shall be used: Echo cancellation (ECH) and Time Compression Multiplex (TCM).

Modem

modemsdial-up modem56k modem
Echo cancellation is important technology allowing modems to achieve good full-duplex performance.
The 201A operated half-duplex at 2,000 bit/s over normal phone lines, while the 201B provided full duplex 2,400 bit/s service on four-wire leased lines, the send and receive channels each running on their own set of two wires.

UMTS

WCDMA3GUniversal Mobile Telecommunications System
The Chinese TD-LTE 4-G, TD-SCDMA 3-G mobile communications air interface. UMTS 3G supplementary air interfaces TD-CDMA for indoor mobile telecommunications. Most cellular systems, including the UMTS/WCDMA use frequency-division duplexing mode and the cdma2000 system.
UMTS-FDD is an acronym for Universal Mobile Telecommunications System (UMTS) - frequency-division duplexing (FDD) and a 3GPP standardized version of UMTS networks that makes use of frequency-division duplexing for duplexing over an UMTS Terrestrial Radio Access (UTRA) air interface.

Duplexer

duplexTR switchTR/ATR cells
Duplexer
A duplexer is an electronic device that allows bi-directional (duplex) communication over a single path.

Push-to-talk

push to talkPTTPoC
An example of a half-duplex device is a walkie-talkie 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 but turns off the receiver, so they cannot hear the remote person.
Push-to-talk (PTT), also known as press-to-transmit, is a method of having conversations or talking on half-duplex communication lines, including two-way radio, using a momentary button to switch from voice reception mode to transmit mode.

Duplex mismatch

Duplex mismatch
On an Ethernet connection, a duplex mismatch is a condition where two connected devices operate in different duplex modes, that is, one operates in half duplex while the other one operates in full duplex.

Repeater

digipeaterrepeatersrelay
The method is frequently used in ham radio operation, where an operator is attempting to use a repeater station.
Since the telephone is a duplex (bidirectional) communication system, the wire pair carries two audio signals, one going in each direction.

List of ITU-T V-series recommendations

V.90V.34V.35
The V.32, V.34, V.56, and V.90 modem standards require echo cancellation.
V.21 is an ITU-T recommendation for full-duplex communication between two analogue dial-up modems using audio frequency-shift keying modulation at 300 baud to carry digital data at 300 bit/s. It is a variant of the original Bell 103 modulation format.

CDMA2000

CDMA1xRTTCDMA 1xRTT
Most cellular systems, including the UMTS/WCDMA use frequency-division duplexing mode and the cdma2000 system.
The designation "1x", meaning 1 times radio transmission technology, indicates the same radio frequency (RF) bandwidth as IS-95: a duplex pair of 1.25 MHz radio channels.

WiMAX

Wireless Broadband4G WiMAXmobile WiMAX
IEEE 802.16 WiMAX
WiMAX profiles define channel size, TDD/FDD and other necessary attributes in order to have inter-operating products.

Crossband operation

cross-bandcross-band carriagecross-band repeat functionality
Crossband operation
Crossband (cross-band, cross band) operation is a method of telecommunication in which a radio station receives signals on one frequency and simultaneously transmits on another for the purpose of full duplex communication or signal relay.

Communication channel

channelchannelscommunications channel
Half-duplex systems are usually used to conserve bandwidth, since only a single communication channel is needed, which is shared alternately between the two directions.
Simplex communication, duplex communication or half duplex communication channel

Four-wire circuit

four-wire4-wire4 wire
Four-wire circuit
The four-wire circuit gets its name from the fact that, historically, a balanced pair of conductors were used in each of two directions for full-duplex operation.