A PBX feature that provides a simple interface for communications between a phone system and a voice messaging system.The PBX sends an SMDI message in advance of each call, advising the voice messaging system of the line that it is using, the type of call that it is forwarding (e.g., call forward, call forward busy or call forward no answer), and the source (calling number) and destination (called number) of the call. SMDI enables the voice messaging system to process the forwarded call more intelligently by accessing the correct personalized greeting associated with the correct mailbox. If the phone is so equipped, the voice mail system can turn on a message waiting light. Alternatively, the voice mail system can send stuttered dial tone in place of normal dial tone when the station user picks up the receiver to place a call, can ring the phone periodically, or use some other method. See also dial tone and PBX.