User's Manual

TT21 Transponder Installation Manual 19 January 2009
00560-00 Issue AA
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5.6.8 External Standby Input
This input, when held low, places the transponder in Standby mode. It should be used to switch
between transponders in an installation with two transponders. The input is active low, and will be
asserted when the voltage to ground is pulled below approximately 4 Volts.
5.6.9 GPS Position Input
The GPS position input is required to support ADS-B functionality. The GPS position input is an
RS232 input to the transponder. The ADS-B features are optional – no GPS is required for normal
Mode S Elementary Surveillance.
The TT21 GPS input can recognise the industry standard “Aviation” format, the NMEA 0183 format,
or the format used by certain Freeflight and NexNav GPS sensors; the interface speed can be selected
between 4800, 9600 and 19200 bps.
There is also an RS232 output on the connector for future expansion. This pin is unused and should be
left unconnected.
5.7 TC20 Controller Electrical Connections
The TC20 controller has a single 9 way D type male connector to link to the transponder, and
optionally to connect to a GPS for baro-aiding.
5.7.1 TC20 Interface - Pinout
Pin Signal Direction
1
Ground -
2
TMAPA Bidirectional
3
TMAPB Bidirectional
4
Altitude Out Output
5
Reserved Input
6
Ground -
7
Remote ON Output
8
Power Input
9
Ground -
The following diagram shows the connector orientation as viewed from the wiring side.
5.8 TC20 Controller Interface Details
5.8.1 TMAP Bus
TMAP is a Trig proprietary bus based on RS485 signalling. It provides a bi-directional interface
between the transponder and the control head. Each TMAP interface comprises a balanced pair of
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