Aviation's Panel Mount Avionics Installation Leader

Trig makes the world’s smallest and lightest Mode S certified GA transponders. The TT21 Trig compact transponder can fit into to the tightest panel space. This allows airplane owners to fit other instrumentation or displays that otherwise might not have been possible.

The TT21 is a two part transponder with a compact control head; this includes an inbuilt altitude encoder - saving further space and expense. A separate hardware box can be installed anywhere in the airframe. The control head can be installed in the panel either as a 2 ¼” round hole or smaller compact mount, the unit ships with the necessary fittings for both install options. The TT22 unit is highly efficient and is ideal for use via an auxiliary battery in gliding or lighter than air flight.

Trig’s TT21 is a popular compact transponder with 130 watts nominal power output. This is a class 2 transponder which meets international standards for 1090ES ADS-B Out (TSO C166b). The TT21 is ideal for use in flight where a light weight Mode S solution is required and is suitable for IFR and VFR use. The TT21 unit is highly efficient and is ideal for use via an auxiliary battery in gliding or lighter than air flight.

The TT21 transponder is easy to operate and with a crisp, bright display it is also easy to read in all lighting conditions. The transponder control head is splash proof too so it’s ideal for open cockpit and seaplane operations.  Mode A and C transponders are now being replaced by Mode S. This technology is more advanced and is optimised for tomorrow’s airspace requirements.

  • Takes minimal panel space, easy installation
  • Integrated altitude encoder
  • Certified class 2 transponder 130 watts nominal output – C166
  • Low weight – 0.8 lbs
  • Low power consumption
  • 1090ES ADS-B Out capable
  • Certified to FAA TSO C166b
  • Unbeatable value and quality – designed and manufactured in the U.K.
  • Two year worldwide warranty

  • Type: Class 2 Mode S level 2els
  • Cerification: ETSO C88a, 2C112b, C166a and TSO C88b, C112c, C166a, approved for IFR and VFR flight
  • Compliance: ED-73B, ED-14F / DO-160F, DO-178B level B, DO-254 level C, DO-260A class B0, DO-181C
  • Supply Voltage (DC): 9 - 33 V
  • Weight: 1.0 lb (450 g)
  • Dimensions (Controller): 63 x 44 x 54 mm
  • Dimensions (Transponder): 62 x 45 x 141 mm

The complete transponder kit includes a TC20 control head, TT21 remote unit, mounting tray, installation kit and manuals.


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Prop 65 Warning: This product may contain chemicals known to the State of California to cause cancer, and birth defects or other reproductive harm.