Which of the following is considered an input device in an electrical system?

In an electrical system, an input device is any component that gathers data or commands from users and sends that information to a controller or processing unit for action. The biometric reader and controller is a prime example, as it scans and verifies individual fingerprints or other biometric data and transmits this information to a system for access control.

The exit button serves as another input device; it allows users to trigger a particular function—like unlocking a door—by simply pressing it. Similarly, a door lock can also function as an input device when integrated with electronic systems, receiving signals that determine if the lock should engage or disengage.

Since all three devices—biometric readers, exit buttons, and electronic door locks—effectively collect input from users to interact with and control electrical systems, they collectively represent the category of input devices. This is why the answer indicating all of the above is accurate, as each choice plays a role in gathering user inputs within an electrical installation.