Duplex (Dx) is a type of transmission in which two data stations with equal rights can send and receive simultaneously via a data link. Duplex transmission is also referred to as two-way operation (according to DIN).
With directional transmission methods, several types of use of a transmission link are possible in principle: directional traffic as simplex, in which information is transmitted in one direction, alternating traffic as half-duplex, semi-duplex, in which the transmitting and receiving directions have different transmission rates, and duplex with simultaneous signal transmissionin both directions. Full duplex connections allow permanent simultaneous transmission of information in both directions without mutual interference.
Duplex transmissions are only possible with transmission protocols suitable for this purpose, e.g. with High Level Data Link Control( HDLC). In duplex mode, transmit and receive operation is performed simultaneously at the interface (DIN 44302).