First-party telephony involves physical coupling at the terminal level, whereby the personal computer( PC) and the telephone are directly connected to each other. The personal computer can be connected to the telephone or to the PBX.
The former architecture is referred to as telephone-centric coupling, the latter as PC-centric coupling. With this type of coupling, the telephone gains access to the PBX or the network via the personal computer. The personal computer is used to control telephone operation. In addition, the personal computer can perform data communication tasks. First-party telephony is also referred to as a stand-alone solution and is supported by the Telephony Application Programming Interface( TAPI).
In third party telephony, the logical connection is at the system level. The personal computers do not control the telephones, but the PBX via a telephony server. In this way, incoming and outgoing calls can be analyzed and assigned to the corresponding personal computers and telephones.