PBX IU IS IVR DATA CCL CTI SERVER PSTN USER n USER 1 USER 2      WS 1 WS 2   WS 3 WS m Agent 1 Agent 2 Agent 3 Agent m A B PBX IU IS IVR DATA PBX IU IS IVR DATA CCL CTI SERVER PSTN USER n USER 1 USER 2      WS 1 WS 2   WS 3 WS m Agent 1 Agent 2 Agent 3 Agent m A B