Which of the following refers to equipment that receives or transmits analog or digital signals?

The correct choice is active equipment, as this term specifically encompasses devices that receive or transmit signals, whether they are analog or digital. Active equipment typically includes devices like routers, switches, transmitters, and more, which are designed to process or manipulate the signals they handle.

In contrast, passive equipment would refer to devices that do not amplify or actively engage in signal processing or transmission. These elements can include cables, connectors, and other components that serve as pathways for signals but do not alter them in any way.

Testing equipment is utilized for the purpose of assessing the integrity or performance of a system but does not itself transmit or receive signals as its primary function. Its role is supportive, focused on measurement rather than facilitation of communication.

Support equipment generally refers to tools and infrastructure that aid the primary operational equipment but are not directly involved in the signal transmission or reception process. This can include racks, housings, and other physical items that provide organization and protection for active devices.

Therefore, active equipment is the appropriate designation for devices that engage directly with the transfer of signals, making it the correct answer in this context.