What type of device responds to input signals and alters them?

A transducer is a device that converts one form of energy into another and responds to input signals by altering them. This can involve converting physical signals, such as temperature, pressure, or light, into electrical signals, or vice versa. The essential characteristic of a transducer is its ability to respond to changes in input conditions and provide a corresponding output that reflects those changes. For example, a temperature sensor transducer converts temperature variations into electrical signals, making it crucial for monitoring and control systems.

In contrast, other devices listed do not primarily focus on this type of energy conversion. A processor, for instance, is designed to perform computations and process data but does not necessarily alter the input signals themselves in terms of physical conversion. An actuator, on the other hand, takes control signals and converts them into physical movement or action but does not specifically alter the signals. A controller manages the operation of systems but does not deal directly with the transformation of input signals into a different form.