The old layout had two set of meters, one for each mainline. When I wanted to change from one power pack on one mainline to the other power pack on the second mainline and keep the train running at the same speed, I would just match the voltage settings on both to the same number and there was no glitch when crossing over. You see, the way I had the old layout wired was with a common so that any of my two main cabs or even the two extra yard cabs could control any engine in any block. It is actually a lot easier than it sounds. No two power packs put out the exact same voltage at a particular setting.
Why would I want all this extra wiring? Because I had two walk-around throttles and with this set up, an engineer could follow and control his train all over the whole layout. Sort of pre-DCC.
The ammeters would tell me immediately if I had a short or open circuit or alert to bad performnce like Mike said.
Now I do not use them as the hand throttles give me all the information I need for each engine.
I was just curious if meters had become a thing of the past, and it looks like they have.
B-)