TT26 ADS-B Transponder Installation Manual
24 January 2017
01633-00
Issue AC
______________________
Trig Avionics Limited
21
computer, or to receive the altimetry data over the link from the controller.
In all three cases the altimetry data will be transmitted from the secondary data
output (either RS232 or RS485, depending on which port is the control port).
This output uses Shadin S format messages at 9600 bps. Only the D, a and b
records are provided, as well as the Shadin checksum.
If the system is configured to use external air data, the input protocol expected
is also Shadin S format.
6.2.2
GPS Source
The transponder has an internal GPS receiver, and that is the primary position
source for ADS-B operation. The GPS data is routed internally to the
transponder and is also transmitted on the auxiliary serial port (pin 7).
The internal GPS can be disabled and an external position source used. In this
case the data input is read from the auxiliary serial input (pin 5); the output on
pin 7 is disabled.
The GPS I/O uses Accord legacy protocol. This protocol is detailed in ES-
GPSBL, “NexNav Mini Nominal Technical Description”.
