Digital refers to a signal that consists of discrete states. A binary signal has only two states, 0 and 1.

Binary being base two numbers with only two possible values, 0, or 1. Primarily used by communication and computer systems.

-see also:
"Digital" is in the NAICS Code "323115"
  (Digital PrintingPrinting, digital (e.g., graphics, high resolution))

"Digital" is in the CPC Code "4523"