Garmin GDL 88 Pilot's Manual page 41

TCAS
TIS-B
UAT
XPDR
190-01122-03 Rev. C
Traffic Collision Avoidance System. An aircraft collision
avoidance system designed to reduce the incidence of mid-
air collisions between aircraft. It monitors the airspace around
an aircraft for other aircraft equipped with a corresponding
active transponder, independent of air traffic control, and
warns pilots of the presence of other transponder-equipped
aircraft which may present a threat of mid-air collision.
Traffic Information Services-Broadcast. TIS-B supplements
ADS-B's air-to-air services to provide more situational
awareness in the cockpit of all traffic known to the ATC
system. The ground TIS-B station transmits surveillance target
information on the ADS-B data link for unequipped targets
or targets transmitting only on another ADS-B link. TIS-B is
a free service available to aircraft operators equipped with
ADS-B Out and ADS-B In.
Universal Access Transceiver. The GDL 88 UAT transmits
ADS-B Out data on the 978 MHz (UAT) frequency. The GDL
88 UAT receives ADS-B, ADS-R, TIS-B, and FIS-B on 978 MHz
Transponder. The equipment which broadcasts aircraft code,
altitude and other information to ground facilities and other
aircraft.
Garmin GDL 88 ADS-B Transceiver Pilot's Guide
7-3