What is an example of a digital input device?

A push button switch is a clear example of a digital input device because it is designed to deliver binary information—either "on" or "off." When the button is pressed, it completes a circuit, signaling a "high" state or activation. When it is released, it breaks the circuit, signaling a "low" state or deactivation. This binary nature is characteristic of digital devices, which are primarily concerned with distinct states rather than continuous values.

In contrast, a thermocouple measures temperature and provides an analog output that varies continuously, making it an analog sensor rather than a digital input device. An analog sensor, by definition, also conveys a range of values, further distinguishing it from the discrete outputs of a push button switch. A frequency inverter, on the other hand, is used to control the speed of an electric motor and operates on principles of variable frequency and voltage, also characteristic of analog operations rather than digital inputs. Thus, in this context, a push button switch stands out distinctly as the example of a digital input device.