OVX300 and OVX303 VTX are based on the Open source project OpenVTX powered by JyeSmith (EpxressLRS team)
OpenVTx aims to provide firmware with both the SmartAudio and Tramp protocols.
Either protocol can be used on the flight controller and on VTx power up the protocol used is automatically detected by OpenVTx.

Currently SA is fully implemented and test against Rev. 09. To date IMRC has not released a protocol standard and implementation is based on information found within Betaflight.

More info and community
https://github.com/OpenVTx/OpenVTx https://discord.gg/uGUKaD2u8Z
Main Features OpenVTX firmware preload Smartaudio ready Nano size and stable power output OVX300

Specifications
Model: OVX300
Frequency: 5.8G 40CH
Transmitting Power: 0/RCE/25mw/100mw/300mw
Power supply: DC 5V
Current (5v): lt;650ma (300mw)
Weight: 0.9gram without antenna
Standard size: 14*15*3mm