It was Märklin that started Z-Scale and because Z-Scale was a German product for a decade, there is a lot of German engineering in the scale. To be sure, things have changed in the intervening years, but at the core of things is a solid engineering design. This design predates Z-Scale, having been developed by Märklin in the early 1950’s for use with their H0 product line. Because the H0 line is AC powered and Z-Scale is DC powered, there are a few differences, but the basic design is pure Märklin. At the heart of this design is a color coded wire and plug system which allowed the model railroader to connect electrical components together. If you follow the color coding standards, you will likely get a reliable outcome. The wire colors are:
- Red - Track power
- Brown - Track ground
- Yellow - Accessory power
- Gray - Accessory ground
- Blue - Activating wires for accessories
Basic electricity requires a complete circuit. For locomotive power, electricity flows from the transformer through the red wire to the rails, through the “red” rail to the locomotive, through the motor of the locomotive, back through the “brown” rail to the transformer. Any interruption to this circuit and the locomotive does not run. So it is with the accessory power, flowing through yellow to a light bulb and back via gray.
In the case of solenoid operated devices such as track switches, uncouplers and relays, the power is controlled through a momentary control box such as the 72720. The yellow wire is connected to the solenoid device, then blue wires connect to the control box, which is connected via the gray wire back to the transformer.
In this situation, electricity is not flowing until a button on the control box is pressed, which then allows current to flow. The solenoid is a coil of wire in the operating device, and when electricity flows through it, a small slug of metal in the accessory is drawn into the coil, which operates the accessory. Turnout points are thrown in this manner, the uncoupler is raised or the relay’s contact points are changed. It is not desirable to have continuous electricity flowing through the solenoid because heat builds up and eventually burns out the coil of wire. So, the 72720 is a momentary device; when you release the button on the control box, electricity stops flowing.
The turnout and the relay both have two solenoids, with two blue wires connecting to the control box. To differentiate between these two wires, one is fitted with green plugs & sockets while the other is connected with red plugs & sockets.