A new air traffic control system has been designed and is now being implemented, in order to alleviate problems in the present system which have resulted from the constant increase in air traffic since 1950. This new system is commonly called the Beacon System, and is defined in a U. S. National Standard. It automatically provides the air traffic controller with an identified three dimensional radar screen presentation of every properly equipped aircraft within his control area. New ground and airborne equipment is required for this system. The airborne equipment required includes an altitude sensing and digitizing device, a 4096 code transponder, and an antenna.