Abstract : The report covers the development of improved surveillance and communication subsystems to meet the demands of the automated NAS/ARTS Air Traffic Control system. Field measurements of the beacon interference environment were completed and studies to upgrade sensor efficiency were intensified. Effort toward the development of a discrete address interrogator with a data link was concentrated upon the core problem of designing the signaling waveforms for both up and down links of the system. Particular attention is being given to system performance in the interference and multipath environment, as well as to system and equipment compatibility with ATCRBS. The project to develop an airborne situation display of NAS/ARTS data has reached the stage for definition of an experimental system. The computer simulated cockpit display has evoked enthusiastic response from experienced pilots and traffic controllers. Preliminary work on the laser beam warning system for Logan Airport was completed with successful demonstration of the prototype hardware in the Laboratory.