Computer Telephony Integration (CTI) | Features/Function Enhancements

CTI had its origins in the early 1980s when AT&T was the first PBX manufacturer to use an adjunct applications processor to provide a message center and directory system function behind its Dimension PBX. Unanswered calls were forwarded to a message center agent who could do a directory lookup for the person being called and enter a message into a computer terminal. The message was then forwarded to a printer close to the called party. The connection between the PBX and the applications processor was a physical link, and no enhanced PBX voice functions were provided. This was CTI in its most rudimentary form.

The concept of enhancing the PBX system with an adjunct applications processor, with physical and logical connectivities between the two independent systems, was not realized until the late 1980s. The first true CTI options were available almost concurrently on two PBX systems. The NEC NEAX2400 and the Intecom IBX offered an Open Applications Interface (OAI) option for third-party application software developers to design applications running on an adjunct client or server to enhance the performance capabilities of the core PBX system. Both suppliers’ OAI option included an intelligent signaling link between the PBX and the adjunct applications processing system. The intelligent signaling link provided a communications path for the PBX system to send system status and message packets to the applications processor and provided the means to transmit the software application program commands back to the PBX. The applications programming interface included with the OAI software developer’s toolkit was proprietary to each system and required software developers to write different programs for different systems. The PBX manufacturers initiated the first CTI implementations, and customer demand for the NEC and Intecom offerings was limited.

When the first CTI industrywide standards were being developed in the late 1980s and early 1990s, it was the major computer companies, such as DEC and IBM, that took the initiative, not the PBX manufacturers. Most of the early CTI implementations were host-based applications, such as predictive dialing and agent screen pops for outbound calling centers. The PBX manufacturers focused on first-party desktop CTI applications by providing a physical/logical link between their digital telephones and desktop PC clients. The client software applications supported a variety of PC telephony features and functions, including directories, screen pops, PBX feature/function activation, on-screen dialing, and call logs/notes. Client/server CTI applications were initially driven by Novell, which promoted its Telephony Services Application Programming Interface (TSAPI) standard. The CTI standard in Europe was developed by the European Computer Manufacturers Association (ECMA) and was known as Computer Services Telephony Applications (CSTA). Microsoft developed its own desktop CTI standard, Telephony Applications Programming Interface (TAPI), that was later enhanced to support client/server applications, and supplanted Novell’s TSAPI as the most popular CTI platform (Figure 1).


Figure 1: CTI system designs

CTI is used behind a PBX system to provide features and functions not available in the generic communications software package. Many of the CTI applications have limited market potential for which PBX developers cannot afford to expend resources. Desktop and client/server CTI was envisioned by many within the industry has a means to replace the proprietary telephone instrument. Instead of buying an expensive voice terminal with limited feature button and display capabilities, the PC client and monitor would serve as the station user interface to the PBX system for all system operations, including dialing, call screening, call answering, and feature implementation. Despite substantial marketing efforts, customers resisted using CTI PC telephony as a substitute for high-performance telephone instruments. Station users were reluctant to learn new programming tools, the ergonomics were poor, the cost was too high, and the PC reliability factor was unacceptable. Desktop CTI shipments behind PBX systems have been negligible, with annual shipment levels less than 2 percent of total station shipments. The only PBX market segment in which CTI gained a foothold was call centers because the evolving call center process became heavily dependent on computer technology, and ACD agents were already using PC clients to handle the typical caller transaction. About 25 percent of call centers are currently implementing CTI.

In the late 1990s several recent PBX market entrants attempted to design and market enterprise communications systems based on CTI client/server architecture principles: an applications processor served as the call processing manager, and station user desktops were analog telephones logically working with PC telephony clients. The desktop PC telephony applications software was included in the system price, and CTI links were used to provide third-party applications not included in the generic software package. These systems did not support multiple-line appearance digital telephones and found limited market appeal. One manufacturer who first attempted to market a pure client/server design, Vertical Networks, recognized the value of digital, multiline, display telephones, and downplayed the CTI attributes of its system when it belatedly marketed a traditional PBX-like digital telephone.

The new IP softphones, available from most longtime and new PBX suppliers, is a proprietary version of desktop CTI, although it is not marketed as such. The PBX system’s call processing manager, be it a traditional proprietary common control complex or a third-party server, functions as a server to the PC client desktop. It is forecasted that IP softphones will become more popular throughout the remainder of this decade, although desktop telephone instruments will remain the dominant voice terminal type.