The eXmux® 3505 has features such as “Hitless Switching” for private ring networks with zero-data-loss path recovery technology, dual path communications for routing redundant paths over public networks and a (DACS) function for cross-connecting DS0s between T1/ E1 circuits and/or eXmux 3501 interface unit. The product is designed for harsh applications and is available in two chassis configurations; a mission-critical model that offers module hot-swap capabilities for all functional cards and a economical compact model for applications where module hot swap capability is not required.Both the 3505 and the 3501 models are interoperable within the same network and and are physically interchangeable.