The following radios and radio boards are compatible with current versions of OpenTX.

Game style version the Taranis:
Black & White LCD 128x64
4 Switches 2 x 3-position, 2 x 2-position
No Pots
2 Sliders
S.Port
Haptic vibration
RAM 128K

Similar to the X12S transmitter with:
Colour outdoor TFT 480x272
8 Switches 6 x 3-position, 1 momentary, 1 x 2-position
3 Pots 1 x 6-position, 2 smooth
2 Sliders 2 rear, 2 front
2 Extra trims
Haptic vibration
Wireless trainer
2 Internal antennas
RAM 8MB

Top of the line transmitter with:
Colour outdoor TFT 480x272
8 Switches 6 x 3-position, 1 momentary, 1 x 2-position
3 Pots 1 x 6-position, 2 smooth
2 Sliders 2 rear, 2 front
2 extra trims
GPS and 6 axis sensors
Haptic vibration
Wireless trainer
RAM 8MB

Smaller version of Taranis Plus with:
Black & White LCD 128x64
6 Switches 4 x 3-position, 1 momentary, 1 x 2-position
2 Pots
No Sliders
S.Port
Haptic vibration
RAM 128K

Tray version of Taranis Plus with:
Color OLED top mounted display for basic telemetry data
Quality 4 bearing gimbals
Bluetooth support
2 Additional sliders
Safe start and safe shutdown power switch
Haptic vibration
Improved audio circuits
RAM 192K

New version of Taranis with:
Haptic vibration
Multi colored LCD background light
Improved LCD display
Improved audio circuits
RAM 128K

ARM Cortex M3 32-bit 120MHz
212x64 LCD with gray scales
60 models + infinite on SD
9 flight modes
Telemetry
Advanced audio functions (voice files from SD, vario, ...)
SD data logger
RAM 128K

ARM Cortex M3 32-bit 36MHz
60 models + infinite on SD
9 flight modes
Telemetry Interface through Futaba trainer jack
Advanced audio functions (voice files from SD, vario, ...)
SD data logger

ARM Cortex M3 32-bit 64MHz
LCD 128x64
6 Switched 4 x 3-position, 1 momentary, 1 x 2-position
2 Pots, 1 with detent, 1 without detent
LCD backlight option
Haptic vibration option

ARM Cortex M3 32-bit 36MHz
60 models + infinite on SD
9 flight modes
Rotary encoder navigation
Telemetry
Advanced audio functions (voice files from SD, vario, ...)
SD data logger

The following radios and radio boards are compatible with legacy versions 2.1.x of OpenTX.

Smaller version of the AR9X board
Upgrade option for the Flysky TH9X and Turnigy 9X
ARM Cortex M3 32-bit 64MHz
LCD 128x64
6 Switched 4 x 3-position, 1 momentary, 1 x 2-position
2 Pots, 1 with detent, 1 without detent
LCD backlight option
Haptic vibration option

Arduino (or clone) MEGA2560 16MHz
30 models + infinite on SD
6 flight modes
2 rotary encoders (one can be used for navigation)
Telemetry
SD data logger

Also exist as Turnigy 9X
Atmega64
16 models
5 flight modes
A lot of mods supported (audio, voice, telemetry, rotary encoder navigation, ...)

ATmega128 8-bit 16MHz
30 models
5 flight modes

ATmega2560 8-bit 16MHz
30 models + infinite on SD
6 flight modes
2 rotary encoders (one can be used for navigation)
Telemetry
SD data logger