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Part# 11-07997
MFR Model# 00225-00-01


Trig’s TT31 transponder is the perfect retro-fit for the popular Bendix King KT76A and KT78A transponders. The TT31 is a certified Class 1 transponder which will ‘plug and play’ straight into the existing Bendix King tray. This significantly reduces both installation time and cost. It provides pilots with class leading Mode S technology that is also 1090ES ADS-B Out capable too (ADS-B functionality requires a Trig tray).

  • Retrofit – ‘plug and play’ installation for KT76A and KT78A transponders
  • Certified Mode S and 1090ES ADS-B Out capable
  • Certified for IFR / VFR flight
  • Lowest power consumption in class
  • 240 watts nominal output
  • Great functionality and performance - TIS traffic capabilities
  • Backlit LED display
  • No cavity tube – no warm up time required
  • No need for dropper resistors
  • EASA ETSO and FAA TSO Certification - includes TSO C166b the latest ADS-B standard
  • Unbeatable value and quality - designed and manufactured in the U.K.
  • Two year worldwide warranty
The TT31 is the most power efficient transponder available today; it’s easy to use and operate, with a clear bright display and simple user interface. Features include a flight timer, stop watch and altitude monitor that can alert you of a deviation from your selected altitude. The TT31 includes data link support for the U.S. TIS traffic service, uplinked from approach radars. TIS traffic can be displayed on a variety of portable displays, and coverage includes most US terminal areas.

Mode A and C transponders are now being replaced by Mode S transponders, technology which is optimised for tomorrow’s airspace requirements. Around the world the introduction of ADS-B surveillance technology means the modern transponder has now become the heart of future airspace compliance requirements. Here the TT31 remains the transponder of choice. The TT31 was the world’s first transponder certified to TSO C166b. This is latest FAA standard for the U.S. 2020 ADS-B mandate and demonstrates Trig’s advanced levels of compliance.

Pilots can buy the TT31 with confidence. Not only is it the easiest upgrade path for their old BK transponder, with a Trig TT31 tray installed the same transponder is mandate ready. The TT31 uses half the electrical power of the leading competitor transponder, whilst still transmitting at a higher signal power, its efficient design reduces waste heat in the avionics stack. This reduces the load on the aircraft electrical system improving overall reliability. The flexible power input means that both 14 and 28 volt systems can be used without special configuration or dropper resistors (we recommend that any dropper resistor fitted for a previous transponder should always be removed). The TT31 is compatible with both parallel and serial altitude encoders; it can even act as a serial altitude repeater to provide a convenient altitude source for your GPS.

The TT31 is popular in the U.S. where a certified WAAS GPS, and a ground air determination device are also required forming the ideal 2020 ADS-B solution. It’s worth remembering that to receive all ADS-B In transmissions in the U.S. the FAA requires a functioning certified ADS-B Out device, so don’t miss out on airspace information - fit a Trig TT31.

All Trig products come with a two year warranty, supported by our global network of Approved Trig Dealers and Approved Trig Service Centers in the U.S. and Australia.

California Prop 65 Warning Symbol

WARNING: Cancer and Reproductive Harm -


  • European Mode S
  • Low Power Consumption
  • No Cavity Tube
  • 240 Watts Nominal Output
  • Plug and Play Installation
  • Backlit LCD Display
  • Easy to Use Rotary Knobs
  • Timer/Stopwatch Function
  • Altitude Monitor
  • Certified 1090ES ADS-B out


  • Type: Class 1 Mode S Level 2 Datalink
  • Certification: ETSO 2C112b, TSO C112
  • Compliance: ED73B, DO160D, DO178B level B, DO181C, DO260A
  • Supply Voltage (DC): 10 – 33 V
  • Typical Current Consumption: Idle: 0.22 A
  • (at 14V) Active: 0.45 A
  • Transmitter Power: 240W nominal at connector
  • Operating Temperature: -20 to +55 C
  • Cooling Requirement: No fan required
  • Weight: 2.98 lbs (1.35 kg)


Unit shipped fast, installed easily. Very happy

November 7, 2019

We had Gwinnett Aero purchase and install in our 79 Warrior. They tied it to our existing Garmin 430W (needed firmware upgrade). They wired the ADSB interface and the Mode S to the Garmin. I now get traffic on the 430 that I did not get before. The ADSB traffic shows up on Foreflight. I am very happy with the price and install.

Pat B
January 24, 2018


Please note,'s personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Does the Trig TT31 MOSE S Transponder require a separate altitude encoder, or is it built in to the Trig?

Per the manual, you will require an encoding altimeter or a blind encoder with either parallel Gray code or RS232 serial output. For best results, and simpler installation, an encoder with a serial output is recommended.

Q: Will it directly interface with my GNS430W?

Yes, the Trig TT 31 (11-07997) will directly interface the GNS 430W.

Q: Will the TT31 (11-07998) interface directly with the Garmin 430/530 systems with appropriate wires added to existing KT-76 tray and connectors, or will you need the new tray (11-07997)?

Yes, the TT31 with software version 3.13 which we carry is compatible with the Garmin 430/530W series for ADS-B compliance. The TT31 will fit in the same tray as the KT-76.

Q: Does the Trig TT31 Mode S Transponder Unit Only - Replacement for KT-76X meet the 2020 ADS-B out requirements? Can the ADS-B in be displayed on my Garmin 430W?

Yes, when coupled to a 430W the TT31 is approved for ADS-B out. For ADS-B in you will need a GDL 39. Certified Aircraft require GDL 88 which is only available at local Garmin dealer.

Q: As a slide-in replacement for my KT76, I assume the aircraft owner could install the Trig TT31 transponder, correct?

A logbook entry would still need to be signed off by an A&P.

Q: Will my Garmin 296 send GPS data to the Trig TT31 to be ADS-B compliant?

No, the Garmin 296 is not an approved WAAS GPS source.

Q: -Does the TT31 has an approved built-in WAAS GPS? -Certified or Experimental installation? -Does it include an adapter to connect to KT78 TSO transponder?

The TT31 does not include a WAAS GPS. The TN70, pn 11-13061, is available to provide WAAS GPS position data to the TT31. It is FAA Approved for installation in certificated aircraft. No adapters are included for interfacing with a KT78.

Q: Will Garmin 496 sending NMEA 0183 GPS data to the Trig TT31 to be ADS-B compliant?

No, the 496 is not an approved WAAS GPS Source. You need an approved WAAS GPS source to ADS-B out compliant.

Q: Does the TT31 work with extended squitter technology (ES)?

Yes, the Trig TT31 will transmit 1090ES (extended squitter).

Q: Is this Trig TT31 xpdr a slide in replacement for a KT 76C transponder?

Yes, per the manufacturer this is a plug and play with the KT76A, KT76C, and the KT78A