SMDI can be used over RS-232 to connect a PBX to a voice mail system. SMDI is an out-of-band signaling which necessitates voice and signaling information being carried on separate paths.
The integration is possible via RS-232 connection because it transports the Automatic Number Identification (ANI) and the Redirecting Dialed Number Identification Service (RDNIS) which are used to indicate the calling party number and the original intended receipent respectively.
SMDI is used to transmit information about call types, reason of forwards, about MWI On/Off states and about error states. SMDI messages are comprised of ASCII characters and symbols.
The PIMG is an eight-port stackable device that provides connectivy and integration between Unity and PBXs.It sits directly between them and emulate digital or analog phones lines to connect with the PBX and uses SIP to connect with Unity over the IP network. Because PIMG connects to the Unity server over an IP Network, it is no longer mandatory to install a voice card into the sever. Also PIMG and PBX can be connected through a IP WAN.
Each PIMG has 8 ports and we can stack up to 9 elements, so it gives us 72 simultaneous voice port connected to a single Unity server.
This type of integration with a PBX relies on the installation of a voice board in the Unity server and it is being somewhat superseded by the use of the Intel PBX IP Media Gateway (PIMG).
The method of integration of the voice board can be realized via:
- Serial interface : In this case, you can configure parameters including phone system manufacturer settings, MWI On/Off codes, serial integration packet settings, COM port settings, voice messaging port configuration settings and so on
- Analog interface : In this case , you can configure parameters including phone system manufacturer settings, MWI On/Off codes, voice messaging port configuration settings and so on
With Serial integration, there are several cabling configurations. The followings are two common one:
- An RS-232 cable directly connects the Unity server and the phone system. So link between the messages lines are direct between the Unity and the phone system.
- An RS-232 cable connects the Unity Server and a PBXLink box and digital lines connect the PBXLink box and the phone system.
When using an PBXLink box, the phone system sends information including the called party extension, calling party extension (if available) and the reason for forwarding to the PBXLink.This communication between the PBXLink and the Unity is performed via Simplified Message Desk Interface (SMDI) packets. Unity activates/deactivates MWIs using analog messaging ports (not the serial which is used).
When using an analog integration, voice messaging lines (analog lines) directly connect the Unity and the phone system and the communication is done this time via DTMF sequences.
When a SIP Proxy Server forwards calls to Unity, it includes the following information:
- The called party extension included in the Diversion Header
- The reason why the call was forwarded in the Diversion Header
- The extension of the calling party (internal calls) or SIP URL of the calling party in the FROM header.
Unity SIP integrations are reliant on SIP for communications and is also reliant on a SIP Proxy Server and a SIP Gateway.
When a call is forwarded by Call Manager to Unity, the following information are included:
- The called party’s extension
- The calling party’s extension or external phone number
- The reason that the call was forwarded to Unity (Busy, No-Answer, Inconditional)
So with these information, Unity is able to route the call to the correct mailbox.