 AIS-P and ADS-B are competing protocols for aircraft based surveillance of traffic, a replacement technology for Mode S radar and TCAS.TailLight implemented as a free addition inside General Aviation ATCRBS transponders, such as the AT-155, utilizes the AIS-P protocol to achieve all intended ADS-B advertised collision avoidance benefits in the airport terminal and en route airspace.It does not interfere with any other avionic systems, produces a system capacity of up to 335,000 aircraft within line-of-sight of each other, and provides interoperability with the other collision avoidance systems, without exposing the aircraft to potential attack.