Give an example of a digital input in a car system.

A door open/closed sensor in a car system is a prime example of a digital input because it operates with discrete states: either the door is closed (often represented as a binary '1') or the door is open (represented as a binary '0'). This simplicity in output allows the vehicle’s onboard computer or electronic control unit to easily interpret the sensor’s signals.

In the context of a car, this digital input is essential for various functions, such as alerting the driver if the doors are not properly closed, which can enhance safety. Additionally, the information from this sensor might be used to control the vehicle's alarm system or to ensure that certain electronic features, like interior lighting, are activated when a door is opened.

The other sensors listed provide different types of data. For example, an engine temperature sensor and an air pressure sensor typically generate analog outputs that represent varying conditions (like degrees of temperature or levels of pressure), which cannot be distilled into simple binary states without further processing. A speedometer indicates vehicle speed and usually relies on similar analog readings or calculations, making it less of a straightforward digital input like the door sensor.