So, if I'm understanding you, there's a TX that moves around the room with a specific source and they get moved to different inputs on the switcher. So in PNM the ipaddress of the TX box is a known value so you can add a TCP/IP client (or several) to your code and put in that IP address. Send the "est/x0D" to the device(s) when the offline indicator(s) goes low and parse out the MAC info.... maybe practice your SIMPL+
Justin Hill