CUCM line
Shared line
Two phones with one directory number are one line appearance shared, not two extensions.
- INVITE — Both phones may ring, depending on the line settings.
- Remote — When A answers, B shows remote in use. B is not a second call.
- RTP — Audio is with A. Privacy and barge are explicit features, not the default media path.
Busy behavior depends on the maximum calls and busy trigger on that shared line. A second call can still ring B while A is talking, until the busy trigger says otherwise.