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The bidirectional attribute means that data is transmitted in both directions from point to point. The term originally comes from radio transmission , in which signals could be exchanged in both directions at the same time. Today the term is primarily used for data transmission, but it is also used as a description of a feature in the process of replicating the genetic information carrier DNA, the replication . The opposite is called unidirectional or, alternatively, monodirectional .

Bidirectional interface

If one interface can both receive ( receiver ) and send ( transmitter ) data , then this interface is bidirectional ( transceiver ). A unidirectional interface, on the other hand, only contains either a receiver or a transmitter.

Depending on the structure of the transceiver, transmission is possible in both directions at the same time or only in one direction at the same time . If data is transferred to the same medium in both directions at the same time, it is necessary to be able to distinguish between them (see full duplex method).

Simple physical interfaces that only transmit information using one variable (e.g. two different voltage levels) often use time division multiplexing . A transmission is only possible in one direction at the same time ( half duplex method).

A point-to-multipoint connection (e.g. conference call ) is not referred to as bidirectional.

In a bidirectional ring that connects several network nodes , the data traffic is usually directed in such a way that both directions of a bidirectional connection cross the same network nodes in opposite directions. In the event of an error in which one of the two transmission paths fails, a protection switchover can take place in the ring so that the interrupted signal travels through the ring in the other direction.


In the case of electronic semiconductors , “bidirectional” means that the current is allowed to flow through them (regularly) in both directions. Such components have no polarity . Each individual connection is therefore both a cathode and, alternatively, an anode . This applies e.g. B. to non-polarized overvoltage protection diodes, so-called non-polarized avalanche diodes or non-polarized suppressor diodes . In the case of non-polar, that is to say bidirectional, protective diodes, there is no ring marking on the side of one of the connections, as is customary with polarized, that is to say unidirectional semiconductor components. The terms "bidirectional" and "bipolar" must not be confused here, because bipolar semiconductors are polarized semiconductors ("two poles" of bi = 2), so each have a unique cathode and an anode and (normally) only allow current to flow in one direction.

Printing technology

In the printing technology of EDP printers or other similar office machines, the term also describes a method in which the printing unit puts characters on paper both in the outward and in the return movement. This means that printing is almost twice as fast as with unidirectional printing. The disadvantage here, however, is often a vertical offset between the two lines that were created with a different printing direction.

Plant engineering switching technology

Motors are switched on bidirectionally when two or more motors are switched on together and not independently of one another.


There are e-cars that have bidirectional chargers. This means that the batteries in such vehicles not only take up energy, but can later transfer it back to any other electric vehicle.