Switches sending messages to the relay-based control logic circuit are what kind of device?

• A. Input
• B. Output
• C. Memory
• D. Control relay

Answer: (A)

Switches sending messages to the relay-based control logic circuit are input devices. In this kind of system, inputs provide the signals that the control logic reads to decide what action to take. When a switch is actuated, it changes the electrical state and creates a signal the logic interprets (for example, on or off). The control logic then uses that information to determine which relays to energize or de-energize, producing the desired output. Outputs are what the logic drives to effect a change, such as energizing a relay or lighting a lamp; memory would store data; and a control relay is an actuator the logic controls, not a source of input. So the switches are input devices because they initiate information into the control system.