You can use a NCE DA-SR, TCS T1 or just about any other hard wired decoder. I used the TCS T1 and the NCE DA- SR. I have 4 of the RS-2's. I personally like to remove the P1K board and hard wire it. I just find it easier to do but that's me. There is also enough room for a Soundtraxx DSD Alco sound decoder. But you have to mill out the fuel tank to put a speaker in there so I haven't tried it except to test fit a DSD I have. I also changed the light bulbs to Miniatronic Yelow-Glo LED's with a 480 ohm resistor. They run great.