When Minitrix came to the market in 1964, there was no “Command Control” such as Märklin Digital, Trix Selectrix or DCC. The Minitrix trains were controlled with Direct Current (“DC”). When you want to change a train’s operating direction, you flipped a switch, the track polarity changed and the train ran in the opposite direction.
Now, of course, things have changed, but the DC heritage remains in the Minitrix product line, available for those who are reluctant to switch over to command control. There are several devices that enhance the operation of a Minitrix DC layout.
Although not a “device”, and although Minitrix does not manufacture overhead catenary wires, the use of catenary wires allows you to operate two locomotives on the same railroad at the same time. At least one of these locomotives has to be an electric type, and both could be electrics if that is what you want.
Key to this type of operation is fitting the railroad with catenary; in Europe, there are at least two manufacturers of catenary for N-Scale; Vollmer and Sommerfeldt.
Also key to successful operation is paying attention to the color coding of the Minitrix wiring system. “Red” and “Blue” are the track power colors. In a catenary installation, one transformer controls both rails, with a blue wire going to the “Blue” rail” and a red wire going to the “Red” rail. The second transformer also has a blue wire connection to the “Blue” rail, while the red wire is connected to a terminal mast which feeds power to the catenary overhead.