resistor of less than 3 ohms. As voltage drops, a motor will slow and ultimately stall. With current limiting, the higher the stall current, the lower the voltage. Leaving a loco decoder on full throttle with the loco stalled may be hard on the decoder and/or the motor, but the voltage will be low enough to prevent serious damage. The resistance of a HO scale loco motor is somewhat greater than 3 ohms, which means the stall current will be less than 1.4 amps. Most decoders can survive this condition.