<Table> <Tr> <Td> </Td> <Td> This article includes a list of references, but its sources remain unclear because it has insufficient inline citations . Please help to improve this article by introducing more precise citations . (September 2015) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article includes a list of references, but its sources remain unclear because it has insufficient inline citations . Please help to improve this article by introducing more precise citations . (September 2015) (Learn how and when to remove this template message) </Td> </Tr> <P> 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 a communication "two - way street" 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). </P> <P> In a full - duplex system, both parties can communicate with each other simultaneously . 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 . The earphone reproduces the speech of the remote party as the microphone transmits the speech of the local party, because there is a two - way communication channel between them, or more strictly speaking, because there are two communication channels between them . </P>

In which mode the communication channel is used in both directions at the same time