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The 4-amp rating is important. Thanks for pointing it out to me (I probably needed the reminder!) and others who might not have known. When I run an LGB loco as described earlier it typically draws 1-2 amps. In addition, I use a 3-amp fast-blow fuse to protect the AIU relay ports.

In an earlier answer to your question about power supplies the possibility of rectifying the output of a variable channel of a TIU powered by a AC power source was suggested. That way the rectified CD output could be used to control the voltage to the track and vary the speed of a locomotive. That setup alone would not give control of the direction of the loco. However it is a simple matter to put the DC output through two appropriately wired AIU switches to reverse the polarity of the DC voltage and the direction of the loco. The two AIU switches have to be linked as a scene for switching voltages plus and minus voltages simultaneously. I run LGB locos with my MTH controller this way all the time.