Abstract: A motor control for exercise treadmill having an AC motor is disclosed which includes various features to enhance operation of the treadmill. These features include a motor control that can vary by shifting or staggering the phases of drive signals applied to the motor in order to reduce treadmill frame vibration. The features also include having the motor controller increase the slip of the motor to improve low speed operation of the motor and to increase the amperage of the drive signals when the motor is operating at a given speed in order to maintain that speed. In addition, a power factor control circuit can be used to increase the efficiency of the motor.

Abstract: An apparatus and process combining an excavation apparatus with a fully contained underground elongated conductive object detector capable of selectively detecting underground objects such as water pipes and electrical cables. The combination of this invention may be advantageously used in trenching to prevent damage to underground water pipes and electrical cables by detecting their presence before the digging implement damages them. An audible or visual signal may be activated and/or the excavation apparatus may be automatically shut down upon detection of an underground pipe or cable a few feet below the excavation. The detector may be incorporated in the digging shovel of a backhoe or maintained in position adjacent the digging implement by a boom extending from the excavation apparatus. Simple and sturdy time gated electronics is advantageously used to differentiate underground pipes and cables from other underground metal debris and to provide range and direction information.