What is it called when signaling occurs over a separate path from the path carrying the analog voice signal?

Out-of-band signaling refers to the method where signaling information is transmitted over a different channel than the one being used for carrying the actual voice or data signals. This approach enhances the efficiency and reliability of communication by separating control signaling from the media stream. This allows for improved management of the communication session and can lead to more advanced functionalities, such as seamless call setup, processing, and teardown.

In contrast, in-band signaling would transmit control information over the same path as the voice traffic, which can lead to congestion and potential loss of control signals. Other options, such as DTMF (Dual-Tone Multi-Frequency) and Centrex, relate to specific signaling types or systems within telecommunication, but they do not describe the concept of using a separate path for signaling. Thus, out-of-band signaling is the right term that accurately describes this method of communication.