• 3.2.1. Unified API

3.2. PBX Integration Features Supported

PBX Integration boards incorporate both circuitry and firmware to integrate applications with specific PBXs. The Unified API, used with the PBX Integration board, enables programmers to more easily develop a single application capable of supporting multiple manufacturer's PBXs. The Unified API also enables applications to access the important digital information sent between a PBX and its station sets. This information is useful in a variety of applications including Voice Mail and Call Center.

3.2.1. Unified API

The Unified API (Application Programming Interface) allows a single application to function on a variety of manufacturers switches. Functioning as an extension to the Dialogic standard voice API, the Unified API offers a single design model that allows developers to take advantage of advanced PBX features (such as called/calling number ID and ASCII display information).

• Called/Calling number ID - usually two sets of digits representing either a trunk line or an extension. This is not to be confused with caller ID received from a CO which provides the telephone number of an outside caller. It is important for an application to know where a call originated and to what extension it is intended. When a call is transferred (or "bounced") through a PBX, this information may be needed by an application at the final destination. If it is not present, the originator (if they are still connected) will have to re-enter the information.
• Retrieve LCD/LED prompts and indicators - Different PBXs have different types of prompts and indicators that relay status information of the station set. By capturing and processing this data, an application can "see" what prompts or indicators have been set.
• Read displays - There are many types of information displayed on a phone; for instance, hook state, messages, features, and other ASCII text. By capturing and processing this data, an application can "see" what is on the display. This is useful for determining the state of the PBX Integration board. Also, when ANI and DNIS digits are available through the PBX, the CO caller ID can be obtained. Display data is also useful when programming a PBX. Because the PBX Integration boards allow applications to "press" buttons, applications can be written to program the PBX in the same way as using a station set to program the PBX.
• Accessing PBX features using dial strings - The PBX Integration board allows applications to access features that are available through a station set. These functions include call transfer, hold, setting the message waiting indicator, and dialing programmable keys.
• Disconnect supervision - When a PBX detects a hang-up from one of its extensions, information is passes to the CO, which in turn hangs up. Typically this is accomplished using a loop current drop. However, if the CO hangs up first, a loop current drop is sent to the PBX but is not passed to the station set. Instead, the station set receives a disconnect message. The PBX Integration board interprets this disconnect message as a loop current drop event. Not all PBXs support disconnect supervision.

Utility functions included in the Unified API allow programmers to control the PBX Integration board. Your application can retrieve the PBX Integration channel and board type, obtain and set PBX Integration channel and board parameters, start and stop the D/42 driver, retrieve D/42 firmware/driver/library version numbers, and retrieve error information.

By using the Unified API to determine the type of switch that the PBX Integration board is connected to, programmers can create an application that can provide specific control for each PBX. Specific control is accomplished using dial strings. Some examples are call transfer, call forward, message waiting light manipulation, and pressing console buttons. The PBX Integration board is capable of performing most functions that are available to a telephone connected to the PBX.

Developers who wish to continue designing switch-specific applications can continue to do so, as the Unified API also provides access to lower-level function calls made available through each individual switch protocol. And for customers unwilling to shift from older PBX integration development models, the Unified API provides for backward compatibility, preserving their development investment.

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