User's Manual

TT21/TT22 Transponder Installation Manual 13 July 2009
00560-00 Issue AF
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Page 18 Trig Avionics Limited
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 signals, called A and B, both of
which must be connected for communication to work.
TMAP A and B lines on the controller should be connected to the
corresponding A and B lines of either TMAP1 or TMAP2 on the TT21/TT22.
5.8.2 Altitude Out
The TC20 incorporates an altitude encoder. Certain GPS receivers can benefit
from having altitude information supplied to them. The TC20 reports pressure
altitude on this pin as an RS232 serial data format, at 9600 bps, using the
format commonly called “Icarus” or “Garmin” format.
5.8.3 Remote ON
This output is connected directly to the Power/Mode switch on the TC20, and
should be connected to the Power ON discrete input of the TT21/TT22.
5.8.4 Power
The TC20 uses 6.5 volts which is available from the TT21/TT22 transponder.
This input should NOT be connected to aircraft power.
5.9 D Connector Crimp Terminals
The 25 way and 9 way connectors supplied with the TT21/TT22 installation kit
are MIL standard versions of the popular sub miniature D type connector
family, and use individual crimp terminals and a receptacle. The MIL
specification for this family of connectors is MIL-C-24308. We supply crimp
terminals because these are more reliable than soldered connections, and are