ight mean complete success (the call went though), progress has been made (the other end is now ringing) or failure (the di- aled number is busy or was not answered.) This information must be provided on a real time basis as the events occur. The application design has to allow for real life situations, for example, peak times when all the outside lines The Telecom Handbook 161 CONVERGENCE OF VOICE & DATA may be busy or heavy users who switch back and forth between several calls on hold. People have come to expect almost instantaneous response from their telephone systems. The Computer Telephony applica- tion must deliver based upon that expectation. Call Control expects the application to act as if it were a tele- phone set. Anything that the telephone can do, the application can now do, too. There are two approaches to Call Control: FIRST PARTY CALL CONTROL The basic premise of first party call control is that the Com- puter Telephony application is acting on behalf of a single user. The application runs on the user's desktop PC. There is a physi- cal connection between the application, the user's desktop computer and the user's telephone line. Figure 7.3 First Party Call Control 162 The Telecom Handbook CHAPTER 7 The desktop computer may connect (with a cable) in front of the telephone, behind the telephone or may actually replace the telephone. The point is that the application is acting on behalf of this one user only. Through the application, the user controls the telephone call. Examples of this include Personal Name, Address and Telephone Number Directories, Personal Answering Machine and Personal Call Accounting (tracking calls made and received). A standard for first party call control is called TAPI (Tele- phony Application Programmer's Interface) for a PC running Windows. Other First Party Call Control standards often found in Call Centers include JTAPI (Java) and S.100. THIRD PARTY CALL CONTROL The premise of third party call control is that the Com- puter Telephony application acts on behalf of any 