As the government transitions to the use of GOSIP and other industry interface standards, provision must be made for cost effective interoperability with existing DOD systems. The TRI-TAC system developed in the 1970's is now being fielded. At the same time there is increasing emphasis within the Air Force on the utilization of cots equipment, and proliferation of COTs based workstation/PC equipment. The TRI-TAC standard digital interface is based on a conditioned diphase TRI-TAC standard which is incompatible with standard commercial digital interfaces. The interface options for cots workstation/pcs, terminals and adp equipment has been limited to the use of voice terminal data ports or limited digital multiplex ports, with limited flexibility and cost impacts. The proposed research program will develop an embedded TRI-TAC CDI interface for Air Force standard workstations/PCs which will allow direct connection through the TRI-TAC communications resources. The Phase I effort will develop baseline prototype design and investigate requirements for future evolutionary enhancements to the baseline device in the areas of signaling. CCEP encryption, and ISDN. The WS/PC TTI solves an immediate problem for application of this class of equipment, and provides the basis for application to other unique interfaces as well as evolution to support future government/ commercial requirements .