Module and remote seem to communicate, but..........

[Brian H]

I have also seen RR501s on EBay and Amazon. Usually around $30-$45.
You could also check some of the indpendent on line X10 dealers for their TM751s and ask them if they are made before X10 removed the switched outlet for a always On version.

As long as you are using Unit 1 for your HR12s command. Either one in your photos setup would work. If you are using unit 9 then only the RR501 would do it.

Personally I like a RR501 over a TM751 anyday.

You may want to see if the relay is dirty as Jeff mentioned. The RR501 is the easier of the two transceivers to disassemble.