What type of systems utilize signals to adjust operations without human intervention?

Automated systems are specifically designed to operate with minimal human intervention by utilizing various signals to adjust their operations automatically. These systems employ sensors, controllers, and actuators to monitor conditions and make real-time adjustments. For instance, in a refrigeration system, temperature sensors can signal the compressor to turn on or off based on the temperature of the refrigerant without requiring any manual input.

In contrast, open loop systems do not use feedback to adjust their operations; they function on a predetermined set of instructions and do not respond to changes in the environment. Feedback-controlled systems do use signals and feedback to maintain desired operational parameters, but the emphasis in the question is on the overall automation aspect, making automated systems the clearer choice. Manual systems, on the other hand, rely entirely on human input to operate, lacking any automated signals or adjustments.