Unity Call Handlers

Unity uses Call Handlers to precess and forward call based on input from users. Call handlers consist of a specific set of instructions or actions that enable Unity to answer calls, plau a greeting, prompt callers, take messages, provide recorded information, and transfer calls.

There are several default Call Handlers in Unity (which are undeletable) including:

  • Opening Greeting
  • Operator Greeting
  • Goodbye

Also Interviews Handlers and Public Distribution are some other Call Handler form.

Digital PBX Adaptor – DPA

The digital PBX Adapter (DPA) voice mail gateways are designed to allow integration of Octel voice mail solutions with Call Manager. DPA uses SCCP to communicate with the Call Manager. It converst DTMF tones to SCCP to enable the communication between the Octel voice mail system and Call Manager.

The DPA will appear on the Call Manager as a collection of  24 IP Phones and the 25th is used to transmit MWI commands. DPA voice mail gateways communicate then with the PBX and Octel voice mail system using the 24 stations lines configured.

Note that there are two other alternative methods of integrating Call Manager with the Octel solutions ( or SMDI solutions):

  • Using a direct SMDI connection between Call Manager (uses of the COM port) and the voice mail system with analog FXS/T1 CAS E&M ports gateway (WS-X6624, VG224). On the Call Manager, the CMI service intercept calls forwarded to voice mail and sends then SMDI messages on the COM port to the voice mail system.
  • Using a VG248, and in that case , the Call Manager connects to the VG248 using SCCP. So the VG248 connects diretly to the voice mail system using an async port for SMDI and analog FXS ports.

SMDI Messages for MWI On/Off

Here are the format of SMDI messages used with MWI On/Off :



OP is used to indicate that MWI should be turned on for the specified station number and <^D> indicates an end of transmission.



RMV is used to request that MWI should be turned off the the specific station number

SMDI Messages for Direct and Forwarded Calls

As expalined in the previous post, SMDI messages are a set of ASCII characters and symbols so we can easily understand the structure of the messages.

Direct Calls

<CR><LF> MD “md-num” “md-port” “fwd-type”<0X20>”src-num”<0x20><CR><LF><^Y>

Here is the explanations of all elements

  • <CR> : Carriage Return
  • <LF> : A Line Feed
  • MD “md-num” “md-port” : Message Desk Number (usually 001) and Message Desk Port (a port between 0000 and 9999)
  • Forward-type : Indicates the forwarding type, D is a direct call
  • <0X20> : ASCII space
  • “src-num” : the number of the station from which the call originated (ANI)
  • <^Y> : Control Y

Forwarded Calls

<CR><LF> MD “md-sum” “md-ports” “fwd-type” “fwd-station”<0X20>”src-num”<0X20><LF><^Y>

So the new fields are

  • “fwd-type” : As previously mentionned, this indicates the forward type but in this case, the type can be A (All cals), B ( Busy), N (No-Answer) or U (forwarded for unknown reason)
  • “fwd-station” : The RDNIS (original called party number)
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