The Cisco T1/E1 circuit emulation service modules (CESMs) are designed for use with the MGX 8220 edge concentrators, MGX 8230, MGX 8250 and the MGX 8800 series wide-area edge switches. The CESM-8T1 and CESM-8E1 offer eight T1s or E1s for structured and unstructured circuit services over an ATM backbone for the new world of data networking. The MGX T1/E1 CESM service modules provide eight T1 or E1 circuit interfaces, with full support for structured (channelized) and unstructured (unchannelized) data transfer modes for circuit emulation services over an ATM backbone.