You see, controlling a DC motor s speed is not as easy as varying its supply voltage. The motor loses torque (power) as the voltage is lowered and finally stops rotating. The MSC1 uses a technique known as Pulse Width Modulation - PWM - to control speed. This is the same system used on electric cranes, buses and subway cars. With PWM, the motor receives full voltage whenever energized - however, the duration of the voltage changes; it's sort of like flipping an on/off switch very rapidly! The motor rotates smoothly and with full power - no matter what the speed. The MSC1 will control DC motors from 3 to 50 volts at up to 10 amps! Complete instructions detail how the PWM circuitry operates and some hook-up ideas. Assembly takes only an hour or two. Kit operates on 9 to 12 VDC and controls motor supply of 3 to 50 volts. Includes our custom case set measuring 5 W x 1 1/2 H x 5 1/4 D.