Which component is typically wired to 24 VAC in the workstation input circuit?

• A. Normally open push buttons
• B. Indicator lamps
• C. Relays coil
• D. Power supply module

Answer: (A)

The key idea is that input devices in a 24 VAC workstation circuit are designed to generate a signal when a user acts, while staying inactive by default. Normally open push buttons fit this role perfectly: they present an open circuit until pressed, at which moment they close and send a 24 VAC signal to the PLC input. This gives a clear, safe, momentary input whenever the button is pressed, with a defined off state when not pressed.

Indicator lamps are outputs used to show status, not to provide an input signal. A relay coil is also a load powered by the circuit, typically controlled by an input or output, but it isn’t the standard user-actuated input device. The power supply module supplies the voltage, not the component that creates the input signal.

So, normally open push buttons are the typical 24 VAC input devices because they switch the signal on when actuated and remain off when not pressed.