This document defines the Air Traffic Control Transponder (ATCRBS/Mode S) with that supports emerging Automatic Dependent Surveillance - Broadcast (ADS-B) requirements. Supplement 4 adds ADS-B Out capabilities and enables the Mode S Transponder to comply with Mode S Transponder MOPS (RTCA DO-181E and EUROCAE ED-73E) as entered into ICAO Annex 10 Volume IV and ICAO Doc. 9871.