Which abbreviation corresponds to Digital Input?

• A. Digital interface
• B. Digital input
• C. Direct input
• D. Data input

Answer: (B)

In control systems, digital input refers to a discrete on/off signal coming from a sensor or switch that the controller reads to make logic decisions. The abbreviation for Digital Input is DI, and you’ll often see labels like DI1, DI2 on wiring diagrams or controller modules. This distinguishes binary, 0/1 signals from analog signals, which carry a range of values and use different inputs (like AI for analog input). Digital inputs are used for things like door switches, pushbuttons, or occupancy sensors and are read by the controller to control logic, interlocks, or sequences.

Other options aren’t standard abbreviations in building automation: Digital interface isn’t a typical label for a discrete signal, direct input isn’t commonly used, and data input would be too generic and not specific to the binary sensing context.