In this paper, we analyze the blocking probability of a call in a PC communication network. In a PC communication network, a call generated from the PSTN (public switched telephone network) requests the connection to the ICPS(information communication processing system) which interconnects the the PSTN and the PSDN(packet switched data network). Then, as a second step, a packet call is requested to the specific service database attached in the PSDN. The call blocking probabilies are analyzed for these two interface points, the PSTN interface ports of the ICPS and the PSDN interface link of the database. We also present some numerical results to show the effects of the system parameters on the performance of the network. The results show the effects of the capacity of each interface point on the performance point.