Trig TT21 Mode S Class 2 Transponder | Complete Kit – Certified



The innovative design of the Trig TT21 transponder saves both space and weight while delivering certified performance. The transponder kit comes in two parts: a compact control head that includes a built-in altitude encoder and a separate hardware box that can be installed anywhere in the airframe.

Trig TT21 features a low 130-watt power output that qualifies this unit as a Class 2 transponder, suitable for aircraft cruising slower than 175 knots and operating below 15,000 feet, IFR or VFR.

Trig TT21 transponder showcases simple operation and a clear and bright display, with manual dimming, which makes it easy to read in all lighting conditions. The TT21 control head is splash proof making it ideal for operations in an open cockpit and seaplane.

Estimated delivery: April 23rd - April 26th
Part Number: 00710-00 Category:

Trig TT21 Mode S Transponder – Minimum Panel Space and Maximum Benefit

Chosen by pilots around the world Trig’s TT21 compact transponder fits in the tightest panel space. The TT21’s innovative design saves both space and weight whilst delivering certified performance.

Customers in the U.S. should be aware that FAA, Federal Aviation Regulations (FAR) 91.227 requires that a compliant ADS-B Out solution use a Class 1 transponder. Trig TT22 is a Class 1 device and meets this requirement. The TT21 is a Class 2 device and does not meet this regulation.” The FAA has stated that Class 1 transponders must be used to be 2020 compliant. For this reason, we recommended the Trig TT22 transponder unit if ADS-B compliance is required. 


  • Class 2 Mode S and 1090ES ADS-B Out capable
  • 130 watts nominal output power
  • Compact form factor – fits in a compact or standard 2-1/4 inch instrument hole
  • Minimal depth – create space in your panel for other avionics
  • One-handed operation
  • Single press VFR button
  • Rapid Squawk selection
  • Display features tail number and flight level for reference
  • Integrated altitude encoder
  • Certified for IFR and VFR flight
  • Manual dimming feature (adjustable backlight)
  • Splashproof, ideal for open cockpit and seaplane
  • Low power consumption
  • FAA TSO Certification – TSO-C166b the latest ADS-B standard
  • Free FAA ADS-B STC for 576 aircraft types
  • Two-year warranty from date of install, U.S. based technical suppor
Trig TY91 and TT22 in Waco Panel
Trig TY91

Product Design

Trig TT21 compact transponder comes in two parts – a compact control head that includes a built-in altitude encoder, saving further space and expense. A separate hardware box can be installed anywhere in the airframe.

The mounted control head takes up the minimal depth in the panel and can be fitted using a 2 ¼” round hole or smaller compact mount – the unit ships with the necessary fittings for both installation options. Trig’s compact transponders are simple to operate and feature a crisp, bright display – easy to read in all lighting conditions and equipped with manual dimming. The transponder control head is splash-proof too, so it’s ideal for open cockpit and seaplane operations.

One-handed operation is easy; the superior interface allows the rapid selection of Squawk code. A single press VFR button and ident button further eases operation. The display also features your tail number and flight level for ease of reference.


  • Control head
  • Transponder unit
  • Mounting tray
  • Install kit
  • Installation and user manuals
Trig TY91

Additional information

Weight0.8 lbs

Controller: 1.8 x 2.4 x 2.1 in (44 x 63 x 54 mm)
Transponder in tray: 1.8 x 2.6 x 6.2 in (48 x 68 x 160 mm)


Transponder Class 1 Mode S level 2els ADS-B Class B1


ETSO C88A, C112C, C166A TSO C88b, C112c, C166b
Approved for IFR and VFR flight


ED-73C, DO-160F, DO-178B Level B, DO-254 Level C, DO-260B, DO-181D

Supply Voltage

9 VDC — 33 VDC

Typical Current Consumption

Idle: 0.15 A, active: 0.34 A @ 14 VDC

Nominal Transmitter Power

250 W at connector

Operating Temperature

Transponder: -40°C to 70°C
Controller: -25°C to 70°C

Cooling Requirement

No Fan Required

FAA 2020 ADS-B airspace compliant capable




Trig TT22 Mode S Transponder

Trig TT21 Mode S Class 2 Transponder | Complete Kit – Certified


Add to Cart