The ADTRAN Dual DSU III Module is one of several expansion modules for the TSU multiplexer family of products. This module should be selected when the customer's data terminal equipment (DTE) needs to be connected to the Digital Data Service (DDS) or the Switched 56 network using a T1 line. The module installs in the expansion slot of the TSU and is subject to the unit's operation and control. A plug-on version of the Dual DSU III is also available for any of the other TSU expansion modules. Both the expansion module and the plug-on module provide two DTE interfaces each. Configuration is available from the front panel of the TSU or by the optional T-Watch PRO management software. Monitoring, performance requests, and testing functions are initiated from the front panel. Each unit provides two separate all rate DSUs supporting synchronous and asynchronous data rates. The synchronous rates supported are 2.4, 4.8, 9.6, 19.2, 38.4, 56, and 64 kbps. Asynchronous data rates are provided from 2.4 to 19.2 kbps, 38.4 kbps, and 57.6 kbps. The DTE interface can be selected as either EIA-232 or V.35 for all data rates. Additional features of the Dual DSU III module include a DTE-to-service rate matching feature for both dedicated and switched modes, and various anti-streaming time-out values used to disable streaming terminals on a multi-point circuit. Private networks and modem tail circuits can be accommodated through clocking/timing options. In Switched 56 mode, dialing options include manual dialing, redialing, and dialing of stored numbers. Dialing over the DTE interface is supported by use of an AT command set or the V.25 bis in-band dialing protocol. The unit responds to standard loopback commands from the telephone company central office. In addition, the user has several built-in test functions. These include V.54 remote loopback, 2047 and 511 BERT test patterns, and four DDS stress patterns--results of which are displayed on the TSU front panel. These features, backed by the quality, service and support you expect from ADTRAN, make the DSU III module an excellent choice for sub-rate access for T1 networks. The Dual DSU III module is one of many application-specific modules available for the TSU 100e, TSU 120e and the TSU 600e. The ability to combine different expansion modules with plug-on units provides a variety of interface port combinations for voice, data, dial backup and video applications.