I thought the SR751 only repeated RF commands received back to RF. If bubbah is trying to send an RF command from either location, then the SR751 would make it seen in both locations. If he wants to send a PLC command from one location and have it seen in the other location, it is my understanding that the SR751 won't help UNLESS you have your CM15A (or other controller) set to send the signal via RF.
Correct the SR751 only repeats RF.
thus it can extend only RF.
Bubbah made no indication of wishing PLC signals a RF transciever would be needed at both locations.
As they stated
There is stubbed up power about half way between & I would plan to plug in one SR751 in that location & one in each building to daisy chain ...will that work ? TIA !!
Only one SR572 should be needed depending on the location of the trancievers at either end.
More details should have been supplied by Bubbah.
If two way comunication is required then the setup would be different then just sending one way for example: a RF signal to a security console