Which device is typically used to switch between automatic and manual modes on a machine?

• A. Pushbutton
• B. Key Switch
• C. Rotary Switch
• D. Selector Switch

Answer: (D)

Switching between automatic and manual modes needs a control that explicitly sets the machine’s operating state and holds that state until changed. A selector switch is designed for this purpose: it provides distinct Auto and Manual positions with a tactile detent and clear labeling, and it is a maintained control, so the knob stays in the chosen position until the operator deliberately moves it again. This makes the mode of operation obvious and prevents accidental changes during operation. Pushbuttons are typically used for starting, stopping, or momentary actions and do not communicate or maintain a mode by themselves. A key switch can unlock or restrict access but isn't primarily used as a day-to-day mode selector. A rotary switch can also select among multiple positions, but the standard and most common device specifically described for choosing a machine’s automatic or manual operation is the selector switch, which is built for clear mode selection and safe operation.