What does the term 'signals' in communication refer to?

The term 'signals' in communication generally signifies a code system designed to convey information succinctly and efficiently, often using specific words or phrases to initiate a particular response. In this context, using numbers preceded by the word "signal" exemplifies a structured method of communication that allows individuals to understand instructions or alerts quickly and effectively, particularly in scenarios that require clarity and prompt action.

This approach is especially useful in environments where time is critical, and misunderstandings could have serious consequences, such as in correctional facilities. By utilizing a standardized code system, personnel can ensure that important messages are communicated without ambiguity, enhancing overall safety and operational efficiency. This cannot be equally said about the other choices, which focus on different forms of communication that do not encapsulate the specific definition of 'signals' as effectively.