The MRC 44 is simply a box with a rheostat, direction switch, and circuit breaker. You need to connect it to the Fixed DC terminals on your power pack (if equipped) as a supply and the output goes to the track. There's a 4 terminal, screw type terminal strip for these connections.
One word of caution, since this is an older style rheostat, it may not control the newer can or low current motors properly. They may go from off to near full throttle with a slight turn of the dial. The dial turn is also only about 90 degrees.
For selecting, you may want to set up a simple A-B switch arrangement.
Does anyone have any comments on something like this. I'm too cheap to go to DCC right now and I ,like to tinker with stuff like this. I have my blocks where I want them, I just need a remote control controller for when I have to walk and spot a car on the opposite side of my layout. Is there a way I could do sort of a "Switch of power" to this device to be able to walk to that one area, even just have it hanging on the side of the layout until I need it.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=110222346414&_trksid=p3907.m32&_trkparms=tab%3DWatching
Any opinions?