Novell AppNote-"Computer Telephone Integration: Call Control
vs. Voice Processing"© Feb 95 FEBRUARY 1995 Computer Telephone Integration: Call Control vs. Voice Processing RICH LEE As technology drives the integration of computers and telephones, there are two main components in the development of this technology which need to be examined and understood. First is call control - the process of setting up and breaking down calls. The second is voice processing - the function of using voice technology in a messaging environment, interactive voice response, converting text to speech, and using speech recognition algorithms to control and access information. This Application Note introduces telephony nomenclatureand depicts the differences between call control and voice processing. Contents
Copyright © 1995 by Novell, Inc. All rights reserved. No part of this document may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, for any purpose without the express written permission of Novell. All product names mentioned are trademarks of their respective companies or distributors. IntroductionThere are two main components of the technology for integrating computers and telephones. First there is call control which is the process of setting up and breaking down calls. Examples of call control functions range from tasks as simple as making a call, to more complex functions such as placing multi-party conference calls, transferring calls, and performing call merge functions. The second component is voice processing; the function of using voice technology in a messaging environment. Voice processing makes use of interactive voice response, converting text to speech, and using speech recognition algorithms to control and access information. This article examines the differences and similarities between call control and voice processing. It looks at the roles of these segments in a computer telephone integration model, and the technological advantages derived by combining the two technologies in a client/server environment. Call Control: A Technology OverviewFrom a definition standpoint, call control is the process of setting up and breaking down telephone calls. While calls can be as simple as an out-dial or make-call, the term also covers more complex tasks such as setting up conference calls between multiple parties, transferring calls, or controlling the receipt of incoming calls. Historically, call control comes from the telecommunications industry, and until very recently call control functions were performed by telecommunication system hardware such as a Private Branch Exchange (PBX), a central office switch, or a key system. along with the actual telephone device sitting on the user's desk. With the introduction of computer telephone integration (CTI), computers--especially micro computers and servers--are now poised to play a pivotal role in performing many of the functions of call control. While the most of today's telecommunications infrastructures are distinct equipment groups, CTI creates a link at the desktop between the user's computer and telephone as shown in Figure 1. Figure 1: This shows the CTI link
between computer and telephone. From a practicality standpoint, this means the function of setting up and breaking down a call is moved from the telephone (a non-intuitive device limited by twelve buttons, and requiring significant knowledge to operate) to the desktop computer (an intuitive device with immense possibilities for specific telephony applications). Once the link between the two infrastructures is established, software applications are developed to run either on the server or the workstation providing the actual user interface for performing call control functions. This is the epitome of Client-Server implementation, concentrating the more expensive components of the hardware base at the server for use by many instead of at the client with expense to many. Call control is achieved in a CTI environment when the user clicks an icon in his windows application (such as a transfer icon), and the computer passes a command to the Telephony Server. Using the Telephony Services library (TSLIB), an asynchronous communications stream (ACS) stream is opened between the client workstation and the telephony server (see Figure 2). The ACS stream is used for all client-server communications between a telephony-enabled application and the telephony server. Figure 2: This shows the Telephone
Services library (TSLIB) initiating an
asynchronous communications stream. Once the stream is opened, information such as destination extension, source extension, etc. are passed to the telephony server using standard Computer Supported Telecommunications Application (CSTA) commands (in this example the API call is cstaTransferCall). The TSAPI.NLM in NetWare is based on the Computer Supported Telecommunications Application "CSTA" industry standard. After initialization, the telephony server takes the CSTA command and through the PBX driver interface, translating the command into the native PBX protocol (such as AT&T's ASAI). The PBX then performs the specified function requested, while the telephony server constantly acts as a multiplexer, routing and controlling the flow of CSTA client or server commands to the PBX. Call Control: An Architecture OverviewThere are three architectures that can be used to achieve call control capability in a CTI environment. Figure 3 shows a representation of each of these architectures from a high level view. These implementation architectures range from simple to complex with increasing capabilities corresponding to the complexity of the architecture. Figure 3: These are the three call
control architectures. Examining the NetWare Telephony Services model, show a new degree of integration between the computer and the telephone, and reveals three main components to the architecture of a call control system:
The link between the PBX and the computing device can be any number of types of physical connections. The most widely used link types include:
The link type used is dependent on the implementation developed by the PBX manufacturer. The server or host computer will typically support any type of physical link from the PBX. The actual hardware is either standard, off-the-shelf hardware (as in the case of an Ethernet link), or is provided by the PBX manufacturer (as in the case of a BRI link). Call Control: TSAPI/NetWare Telephony ServicesTelephony Services Application Programming Interface (TSAPI) is a programming interface developed by Novell and AT&T. TSAPI is based on the Computer Supported Telecommunications Application (CSTA) industry standard. TSAPI plays a significant role in the deployment of call control applications for two important reasons:
Below are two examples of call control applications:
Voice processing is a broad term that encompasses several similar technologies. Included under the heading of voice processing are:
Voice processing provides many user benefits, including:
Figure 4: How voice messaging works in a
NetWare environment. There are also more advanced features of sophisticated voice processing systems. It is important to understand that while many of these features have been available for years, access to them was very limited until PC graphical applications began to provide an interface to manage the resources and allow users to take advantage of the functions. These advanced features include the following:
As an example, we have selected the CallWare voice processing system developed by International Voice Exchange. CallWare is written as a NetWare Loadable Module (NLM) and runs natively on NetWare. A voice processing system consists of four main components:
Figure 5: This provides details of
the board components. Some of the key functions of the voice processing board are:
Figure 6: How the voice messaging system
handles an incoming call sent to a busy extension. Important to the functionality that can be achieved from a voice processing system is the integration between the system and the PBX. This integration, or physical connection, will serve as the pipe through which the signaling between the two systems will travel. In most scenarios, the physical line between the telephone switch and the voice processing server that is used for the voice signal will be a typical analog phone line. But while the analog voice signal is transmitted through the analog line, the data packet signals could or could not be transmitted down the same line. There are two primary methods of addressing this portion of the integration:
Figure 7: This is an example of in-band
signaling.
Figure 8: This is an example of out-of-band
signaling. As a programming interface, TSAPI defines call control functions (making calls, transferring calls, placing calls on hold, and so on). It does not deliver a standard programming interface for voice processing. However, the NetWare Telephony Services NLM does provide several valuable things for voice processing systems:
Interactive voice response (IVR) is a common application for allowing users to gain access to common information via a telephone. The best application example for IVR is the banking industry. A user calls his "automated banking system", is greeted with a pre-recorded prompt "Thank you for calling Sierra West Bank". The user is then prompted to enter an account code and desired transactions using the key pad on the telephone. The IVR system then processes the request and performs database lookups to procure the requested information. The information is then played over the telephone to the user using pre-recorded digitized voice strings. Example: "Thank you Susan Kingston. Your checking balance is $1,345.78." Both the account owner's name and the bank balance were obtained from the IVR system database. The three big advantages to an IVR application are:
A second example of computer telephone integration in the voice processing arena can be seen in voice messaging. Voice messaging, or voice mail as it is commonly called, is the function of sending, receiving, and processing of stored voice messages. The interface to any voice messaging system has traditionally been limited to the telephone. This has presented many user interface problems. Many of these problems are solved by integrating the computer system and telecommunications system. Traditional problems included the following:
With a CTI-based voice messaging application, a user can view the header information of all messages using a PC-based graphical interface. The header information typically shows who the message is from, the date and time the message was left and the length of the message. The user can then select which message to listen to first, second, and so forth. Messages can be sorted simply by double-clicking on the column heading. Message management is simplified by providing a graphical point-and-click interface for play, stop, pause, rewind, fast-forward, reply, forward, record, delete, etc. Even advanced features are greatly simplified. For example, let's say we want to send a message with a specified future delivery date and time (a very useful function so difficult to use in a stand-alone system, that it is most often ignored). In a CTI-based voice messaging system, the user simply clicks the "future delivery" icon, enters in the date and time of delivery, and clicks the send button. With this example, it makes clear the ease-of-use enhancements that are enabled in a CTI environment. SummaryAs detailed in this article, there are strong advantages to the integration of computers and telephones. Within the realm of CTI there are two fairly distinct technologies ( call control and voice processing. Each of these two segments serve a purpose in the overall scheme of CTI. It seems evident that the real advantages, which for the most part are just now beginning to be a reality, are realized when the full power of call control is combined with the sophisticated messaging and interactive capabilities of a voice processing system. Additionally, we immediately see the advantages of implementing Voice Processing with call control. Speech to Text abilities from the telephony server would provide immediate integration with existing email systems and the prioritization of incoming calls, sender verification (who really called), not to mention the ability to voice authenticate. While most users may not need these advanced abilities, they will certainly find their way into corporate culture. |