The ADTRAN ESU LT is a low-cost, fullfeatured E1/FE1 data service unit/channel service unit (DSU/CSU). The ESU LT provides an interface between E1 or Fractional E1 service and the end user s data terminal equipment (DTE) for applications such as LAN-to-LAN bridging, Frame Relay circuit termination, and video-conferencing. The ESU LT provides access to traditional dedicated point-to-point E1 services as well as network termination for Frame Relay.