SAPphone Server 
SAPphone provides an RFC interface that is used to connect external telephony software to SAP Systems. Third-party manufacturers can program a direct connection to the RFC interface or use the SAPphone server delivered with the SAP System. The SAPphone server serves as a nexus between the SAPphone RFC interface and the TAPI standard interface that Microsoft has defined for telephone integration solutions. If the SAPphone server is used, manufacturers of TAPI-compatible telephony products do not have to program an individual connection to the SAPphone RFC interface.
The following graphic shows the components involved in the connection via the SAPphone server:

SAPphone Server 2.5 supports all the basic telephony functions and call center functions of SAPphone. It is downwardly compatible, meaning that you can use it with SAP version 3.1I and higher. Predictive dialing is not supported by the SAPphone Server.