Technical Information on Parma Controllers
Before diving into what's available in controllers and related items, a quick sentence or two is appropriate regarding exactly what controllers are and how they function. The ability to control an H.O. slot car depends completely on a small device called a "hand controller." This pistol-shaped item enables you to control the amount of electrical current that the car receives, and therefore, it’s speed.

It is easy to understand the function of a hand controller if you think of it as nothing more than a simple electrical 'valve.' Take your finger off the trigger and the 'valve' closes completely (no current gets through to the motor). Squeeze the trigger slightly and the 'valve' opens a bit (some current gets through and the car starts to roll). Squeeze the trigger more and the 'valve' opens further (even more current passes through to the motor and the car goes faster) and so on until the 'valve' is fully open and all of the available current is fed to the motor and the car is running 'flat out.'

Inside the hand controller is a resistor, which is simply a ceramic core with wire wrapped around it. When the trigger is depressed, a wiper rubs across the coils on the resistor, picking up more and more current and passing it along to the car’s motor. The resistance to the current trying to pass through the coils is measured in ohms. The thickness of wire and number of coils around the resistor determine its ohm rating. Controllers can get quite hot during a race, especially on tracks with battery power, where controllers have to flow a large amount of current. To compensate for this, 'heat sinks' are used to dissipate the heat rapidly, as well as cooling vents molded into the plastic handle.

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