Garmin GTS 820 TAS Pilot's Manual page 11

Automatic Dependent Surveillance - Rebroadcast (ADS-R) is the rebroadcast
of ADS-B data. ADS-B may transmitted on either 1090 MHz or 978 MHz. ADS-B
In capable aircraft may only be able to receive data on one link. Therefore, a
means to get data from one data link to the other is required. ADS-R is the
rebroadcast of ADS-B data by FAA ground stations and provides this service by
taking data from one link and rebroadcasting it on the other. For example, two
aircraft are in the service volume for a ground station, and one transmitting on
1090 MHz and the other 978 MHz, the ground station will retransmit the data
from each aircraft on the other link to ensure the two aircraft can "see" each
other. The GTS is capable of receiving ADS-B directly on the 1090 MHz data
link only. ADS-R allows the GTS to "see" the aircraft that transmits ADS-B on the
978 MHz data link.
Traffic Information Service - Broadcast (TIS-B) provides a bridge between
the radar based ATC system and the ADS-B based system. When an ADS-B In
capable aircraft is within the service volume of an FAA ADS-B ground station,
the ground station will begin to broadcast a portion of the ATC radar picture
to the aircraft. This aircraft is then included in the list of aircraft that is being
provided TIS-B service and is then considered a "TIS-B participant."
190-00587-02 Rev. E
Figure 2 ADS-R Operation - FAA Illustration
Garmin GTS Traffic Systems
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