PhonSoft Technical Library
Subject:Caller ID, SMDI, ANI
Category:Configuration, MailCall, Unified MailCall

There is a lot of confusion about Caller ID, SMDI, and ANI. Especially Caller ID which is often used as a generic term for called party information. These are all means to get calling and called party information (who is calling, and who are they trying to reach).

There are three basic ways to get calling and called party information.

*** Caller ID

Caller ID is an analog modem protocol which contains ASCII text calling party information inserted between the first and second ring from the Central Office (C.O.) when ringing an analog phone line. (That is why if you pick your home line up on the first ring, you don't get Caller ID. You have to wait until almost the start of the second ring.) Very few PBXs can "read" this modem information. Also, very few PBXs support sending this information in the Caller ID modem format to analog lines. But some do. Some PBXs collect this Caller ID information and can pass it along as in-band digits or SMDI.

Dialogic cards can directly "read" Caller ID information.
- If the Dialogic card is directly connected to the C.O., you will get the Caller ID info.
- If the PBX receives and passes along Caller ID in native format, you will get the Caller ID info.
- If the Dialogic card is inserted behind the PBX (as it normally is), the PBX almost always loses the Caller ID signal and does NOT pass it through. This is the normal business scenario.

Caller ID also has other limitations of showing the actual calling number, which in a business environment is usually one of a large number of outgoing trunk lines and does not easily let you know who is calling. It is almost always different than the number you use to call that person. And it is seldom the same number on successive calls.

However, PhoneSoft fully supports Caller ID.

*** SMDI

SMDI is a serial protocol defined by BellCore for what became Centrex. It is an RS-232 protocol which provides calling party, called party, and called reason information. An extension to SMDI also supports setting and clearing Message Waiting Indicators.

PhoneSoft fully supports SMDI.

Many PBXs support their own proprietary version of SMDI. (Sometimes a subset, sometimes a superset). PhoneSoft can easily reverse engineer any PBX SMDI data stream and support it completely. Or even better, the PBX manuals often describe exactly what is in the stream. In any case, we can easily support any flavor of SMDI.

If you have Centrex lines, you can purchase a ~$5,000 modem box and lease a dedicated phone line over which the phone company will send you SMDI information. The back of the modem box has a standard SMDI serial connection. PhoneSoft supports this completely. Not many large companies run this way any more, but we see it from time to time.

Several companies such as VTG and Calista have external boxes or internal boards which connect to PBX specific digital phone extensions and provide serial SMDI connections with information about the calls. Many voice mail systems use these to get SMDI information. PhoneSoft sometimes uses these as well. They can provide a tighter level of integration than just analog lines when the PBX itself does not support SMDI.

There are two flavors of these boards.
- One kind receives the call on a regular digital extension and then forwards it to the analog Dialogic board. This has a delay of about one second.
- The other kind has both digital and analog connectors and bridges the two lines directly. PBX to Calista board to Dialogic board. This method has no delay.

The other advantage of SMDI is that is gives information exactly when a caller hangs up. This is very useful in PBXs which do not support loop current.

These boards all use standard SMDI and are completely supported by PhoneSoft.

*** ANI

ANI is the called party information passed in a T1 (digital) connection. PhoneSoft fully supports ANI as well.