Type 4110/4120 travel controllers provide reversing/plugging control of
series or compound wound DC motors. The simple easy-to-understand
system has smooth timed responsive acceleration and rectified type
plugging. The motor is started with all the resistor in the circuit.
Contactors in the controller short out the external resistance in timed
steps under control of a master switch, to provide smooth and rapid
acceleration. During reversing, a plugging relay with rectifier
prevents all the accelerating contactors from closing until the motor is
practically at rest. This keeps all the resistance in the circuit
during reversal to provide safe, controlled stopping.