Unlike first-party CTI, where the phone is directly linked to the computer, third-party CTI does not require any connection of this kind. In the case of first-party CTI, there is a direct physical connection between the phone and the computer. With this type of link, a basic distinction is made between the computer-centric and the phone-centric connection model.
In the case of third-party CTI, the computer and phones communicate via a third component, the so-called CTI server. The latter is installed at a central point in the network and linked to the telephone system via a compatible interface. Incoming and outgoing calls are signalled via this interface. In addition, a so-called TC server rather than a telephone system is often used in modern architectures. Although using a CTI server is more complex than establishing a physical link between the phone and the computer in the case of first-party CTI, it results in far more flexible and efficient computer telephony integration. As a prerequisite for the proper functioning of the system and convenient use of the functions available, the network must operate efficiently without errors or delays. Bandwidth bottlenecks or data losses and data congestion can influence and disrupt the use of all company telephone functions. The advantage of a first-party CTI solution, namely faster workstation installation and configuration, is soon lost in the case of large-scale systems with a high number of telephone workstations. Therefore, third-party CTI is particularly suitable for large, high-performance systems.