A Hand-Off-Automatic (H-O-A) circuit requires a selector switch with how many positions?

A Hand-Off-Automatic (H-O-A) circuit is designed to control motors in different modes using a selector switch. This switch must have three distinct positions: one for manual control (Hand), one for the Off state (Off), and one for automatic operation (Automatic).

The Hand position allows the operator to control the motor directly, providing the ability to start and stop the motor at will. The Off position ensures that the motor is completely disabled and cannot operate under external or automatic commands. The Automatic position engages the control system to operate the motor based on pre-set conditions or inputs, such as timers or sensors.

Having these three positions allows for flexibility in operation while ensuring safety by providing an Off state that isolates the motor from control systems and reduces the risk of unintended operation. Thus, a selector switch for an H-O-A circuit must have exactly three positions to serve its intended purpose effectively.