The Discrete Address Beacon System (DABS) is a surveillance and communication system for air traffic control. DABS is under development as an evolutionary replacement for the FAA's existing Air Traffic Control Radar Beacon System (ATCRBS) to enhance surveillance and provide a digital data communication capability. Each DABS aircraft recognizes and responds with a unique code (its discrete address), thus permitting data link messages to and from a particular aircraft to be accommodated integrally with the surveillance interrogations and replies. The FAA i s currently testing a set of data link applications which will provide aviation services for the initial field implementation of DABS. Link formats, ground interfaces, and systems to support a set of data link applications are also being evaluated for inclusion in the DABS field implementation. The initial data link services include ATC coordination messages and ground-to-air dissemination of weather and aviation related information. Uplink ATC messages include Minimum Safe Altitude Warning (MSAW) Alerts, Altitude Assignment Clearance Confirmation messages, and Takeoff Clearance Confirmation messages. These messages provide the pilot with a supplementary visual confirmation of voice communications. The services also include the capability for the pilot to request weather products derived from National Weather Service (NUS) information. The weather products include surface observations, terminal forecasts, winds aloft, pilot reports, hazardous weather advisories and digitized weather radar Information. Real-time surface measurements from the Enhanced Terminal Information Service (ETIS) are also included. The ETIS i s a flight advisory service which provides the pilot information to assist in conducting safe approaches to (or departures from) an airport. It includes information normally provided by the current Automated Terminal Information Service (ATIS) plus additional data such as weather alerts which pertain to the airport of interest. A DABS data link avionics system has been developed for the purpose of demonstrating and evaluating the initial services. It consists of an airborne microprocessor system with a variety of peripherals and interfaces. The microprocessor communicates with the ground-based equipment via a DABS transponder. Data link information included in the uplink interrogations is processed in the airborne microprocessor and then displayed to the pilot. The display device is a time-shared weather radar indicator with a 256 x 256 bit color graphics capability. Other peripherals include a printer, pilot keyboard, altitude alerter, and a multifunction annunciator capable of speech output.