The Challenge of Telephony Integration

Stanford Diehl

The great challenge of computer telephony integration (CTI) is to combine computer-based media technologies (e.g., voice, fax, and speech recognition) with a wide range of often-proprietary telephony equipment (e.g., telephones and switches). Signal Computing System Architecture (SCSA), a standard that's supported by a wide range of CTI vendors, defines a modular architecture for seamlessly integrating computer-based applications with diverse telephony hardware.

SCSA includes both a software and a hardware specification. The SCSA Telephony Application Object (TAO) Framework and the SCSA Hardware Model are independent. The TAO works over a variety of hardware models, including proprietary devices, by implementing a switch-fabric controller. This co ntroller, specific to the underlying hardware, receives resource requests from TAO and translates the request to the specific hardware interface.

The Service Provider Interface (SPI) sits on top of the hardware-specific switch-fabric controllers, providing developers with a consistent interface to different vendors' hardware devices and software components. The SPI enables different hardware and software computer-telephony modules to interoperate seamlessly.

The application worries only about the abstract telephony features it needs from the system, instead of the specific hardware devices that support those features. This design delivers resource and location independence to the application. When an application requests a particular set of features (e.g., a text-to-speech component and a fax line), SCSA creates a group of resources that can service the re quest.

Such a group can contain one or many physical resources. SCSA manages the resources for the application, in effect pooling a diverse set of physical devices into a single, customized system. Once a call or other application event is over, the functional group is destroyed and the physical resources become immediately available to other applications.

Simple fax-on-demand solutions, such as those reviewed here, don't require the rich functionality enabled by SCSA. But vendors such as Copia and Telephone Response Technologies rely on SCSA to integrate higher-end resources (e.g., speech recognition or conferencing) and to negotiate complex switching across multiple lines.

The final result: a portable, cross-platform, hardware-independent architecture for CTI.

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SCSA Architecture

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The SPI provides a consistent interface between telephony hardware and software.