CM15a works with RF but not AHP

[JeffVolp]

X10 commands are comprised of a doublet with two identical halves.  A repeater receives the first half and overlays it in bit sync with the second half.  So only the second half of the command is boosted in amplitude.  No additional commands are sent.  A receiving module only has to receive one half to take action.  If the direct first half is too weak for it to respond, the "repeated" second half should be stronger.

Is that how the XTB-IIR works, too (for both signals coming in the front outlet, and commands received from either phase)?

Both halves of the doublet are boosted for commands sent through the X10 Input receptacle, but only the second doublet for repeated commands.  In that case it error checks the received command before repeating it.

Jeff