Simplified Message Desk Interface
Simplified Message Desk Interface (SMDI) is a protocol that defines the interface between a phone system and a voice mail system. It was developed by Bell Labs. It is used to provide the voice mail system the information it needs to process the call. Each time a call is sent to the voice mail a message is sent using SMDI over a serial interface that identifies the line, the type of call and Calling/Called party numbers. The SMDI protocol also specifies a method for turning Message Waiting Indication (MWI) on and off on individual telephone lines.