The Marine Corps Systems Command (MARCORSYSCOM) is in the planning stage of a procurement for the replacement for its current Unit Level Circuit Switch (ULCS) equipment. The Transition Switch Module (TSM) will provide commercially available circuit switching technology to replace the aging TRI-TAC family of equipment (AN/TTC-42 and SB-3865). It will provide all of the services currently available in USMC switching equipment in a smaller, lighter package. Additionally, the TSM will provide enhanced multiplexing capabilities and an Integrated Services Digital Networks (ISDN) capability. The TSM will provide a flexible Unit Level Switch capability that bridges legacy TRI-TAC switches with current commercial technology to provide Marine maneuver elements with more robust voice/data switching, data transport, and bandwidth management capabilities. The TSM is anticipated to be a three transit case solution that will be fielded to all units that currently have a circuit switching capability (Marine Expeditiona