the inherent theory is one of simple logic really:

Simplex involves only one freq, either party can use it but it is like a
game of ping-ping
only one can transmit [TX] at the same time, the other must listen [RX].

Half-Duplex or more correctly: Split, involves two freqs, but again they
cannot be used at the same time
one station can only TX whilst the other must RX. [but talk-through can be
enabled by a remote base station].

Full Duplex is like a phone conversation, two freqs, both parties can RX &
TX at the same time.

sadly, these terms are often misinterpreted or used to describe radio
systems incorrectly.
esp in scanner listings!


mike


"Robert11" wrote in message
...
Can someone please explain the major differences between simplex, half
duplex, full duplex, etc. ?

What is there inherent in the theory that prevents two way conversation,
like on a phone line, in the simplex mode (such as in maritime VHF/fm ship
to shore conversations) ?

Thanks,
Bob