ACG Certified Commissioning Authority (CxA) Practice Exam

Digital output is the signal type used for binary, on/off control in many controllers. It represents a channel that the system uses to drive field devices like relays, contactors, or actuators, switching between a high and a low state rather than producing a continuously varying value. This distinction—digital versus analog—helps technicians understand what kind of signal to expect from a controller and how to interface with it. The term digital output specifically communicates that the output is a discrete, binary signal intended to actuate a device, not a variable or data stream. The other terms aren’t standard in this context: direct output isn’t a common designation, data output is too generic and could refer to any data channel, and digital optical output would imply an optical signaling method, which isn’t the usual meaning of DO in control schematics.