The newer target has a 5 volt regulator for the detector, there's a terminal block that accesses it and the relay contacts. Mainly meant for the sound card but not much else, the regulator can only source about 100mA, good for the sound card because it has a small current draw. There are solder points to add your own connector for power, I stay away from Tamiaya plugs and use the Deans connectors.

You are right about making it Tamiya only, that would limit its use. I guess shielding it from other sources is the best route.