# What is the definition of half duplex?Is this system,$A$ give $x$ to $B$,then $B$ give $x$ to $C$,called half duplex?

I saw the definition of half duplex in wiki,and it said

half-duplex (HDX) system provides communication in both directions, but only one direction at a time (not simultaneously). Typically, once a party begins receiving a signal, it must wait for the transmitter to stop transmitting, before replying.

However,i saw a paper: http://jultika.oulu.fi/files/nbnfi-fe2019040110636.pdf ,its system model is a transmitter transmit the $$x_1$$ and $$x_2$$ information to the user1(U1),then U1 transmit $$x_2$$ to the user2(U2),and it said this is half-duplex.

So in fact,the definition of half duplex is that device can transmit and receive,but no need to transmit and receive at the same time?

I mean,$$A$$ give $$x$$ to $$B$$,then $$B$$ give $$x$$ to $$C$$,this is also called half-duplex?I thought this is called simplex duplex before,because i thought the half-duplex is $$A$$ give $$x$$ to $$B$$,then $$B$$ give $$x$$ back to $$A$$.

So i want to ask that $$A$$ give $$x$$ to $$B$$,then $$B$$ give $$x$$ to $$C$$,this is also half-duplex?

• This is not related - Half duplex relates only to the communication between two entities - can they transmit and receive in the same time? It is usually a feature of the receiver. – Moti Jul 5 at 6:54
• Half duplex means a device cannot transmit and receive at the same time. It's as simple as that. – BlackMath Jul 6 at 5:51

As you say "$$A$$ give $$x$$ to $$B$$, then $$B$$ give $$x$$ to $$C$$" which specifies that while $$B$$ ls listening to what $$A$$ is telling it (the $$x$$ that is being given to $$B$$), the transmitter in $$B$$'s possession must remain silent until $$B$$ has completely received $$x$$. It is only then that $$B$$ can start up his transmitter and send $$x$$ to $$C$$. So, $$B$$ cannot receive and transmit at the same time, that is, $$B$$ is operating in a half-duplex mode. If $$A$$ were to send $$y$$ to $$B$$ while $$B$$ is sending $$x$$ to $$C$$, $$B$$ just ignore the transmission from $$A$$: $$B$$'s transmitter is active and so its receiver must be in-operational till $$B$$ is done talking to $$C$$.