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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.


  • 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)
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Q: What is needed to make the Trig TT31 ADS-B out compliant?

Part # 11-07998 is a mode S Transponder that is 1090 ES ADS-B out capable.

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