HYBRID TDM AND ATM VOICE SWITCHING CENTRAL OFFICE AND METHOD OF COMPLETING INTER-OFFICE CALLS USING SAME

摘要

A hybrid central office for serving a plurality of subscriber lines while serving as a virtual access tandem to a subnetwork of central offices having a connection to an ATM backbone network is described. The hybrid central office includes a computing module having a messaging interface to the ATM network, an inter--working trunk interface to the ATM network and a trunk connection to the PSTN. The hybrid central office serves as a tandem switch for other central offices connected to the subnetwork. Other central offices are preferably connected to the subnetwork by a signal large trunk group. A11 inter-office call routing is therefore handled by the hybrid central office. The hybrid central office also provides a gateway to the PSTN. Inter-office calls originated and terminated within the subnetwork are set up by the virtual access tandem but after call set up, the virtual access tandem is not involved in the call. The advantage is the utilization of spare processing capacity in a central office to off-load inter-office trunking congestion, as well as a significant reduction in trunking maintenance costs.