The mode; duplex or full-duplex, is a communication where the conversation can take place simultaneously through a device such as the phone.

In a duplex transceiver (or full duplex transceiver) the conversation can take place simultaneously, just like in common telephones, where both parties can talk at the same time.

It differs from half-duplex transmission where the transceiver allows you to let talk are an interlucotore at a time pressing the PTT switch.