The word “Transducer” is the common word used for both Sensors which can be applied to sense a wide range of various energy modes such as transit, electrical signals, radiant energy, thermal or magnetic power, etc., and Actuators which can be utilized to shift voltages or currents.

There are many various types of sensors and transducers, both analogue and digital and input and output ready to choose from. The type of input or output transducer being utilized depends upon the type of signal or method being “Sensed” or “Controlled,” but we can define a sensor and transducers as tools that turn one physical quantity into another.

Tools which produce an “Input” function are usually called Sensors because of the “sense” a physical change in some property that changes in response to some excitation, for example, heat or energy and transform that into an electrical signal. Machines which produce an “Output” function are generally called Actuators and are used to control some external device, for example, movement or sound.

Signal Transducers are utilized to transform energy of one kind into energy of another type, so for example, a receiver (input device) converts sound waves in electrical signals for the amplifier to amplify (a process), and a loudspeaker (output device) converts these electrical signals back into sound waves and an example of this simple.