transceiver behavior wrt relay

[bcboy@xxxxxxxxxxxxxxxxxx]

Ok, so I'm reading about the PIC replacements that have been done on
the RR501, and I came across this:

>> As compared to the original X10 code in which the relay responds
directly
>> to the RF signal from the remote, with your code in the PIC, only
the
>> power line command controls the relay, which of course is a better
>> design.
>
> A free benefit of full-duplex operation...

I don't get it. Why would you want the relay to NOT respond when you
send the RF command for it? Or is the issue here that the RR501
normally doesn't send the unit 1 code on the wire, so other devices on
unit 1 never hear it? Does full-duplex in this case mean that the
modified RR501 puts the code on the wire, then reads its own broadcast
and flips the integrated relay?