OpenVTx 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 . 09. To date IMRC has not released a protocol standard and implementation is based on information found within Betaflight. OpenVTX firmware preload Smartaudio ready Nano size and stable power output OVX303 Model: OVX303 Frequency: 5.8G 40CH Transmitting Power: 0//25mw/100mw/300mw Power supply: DC 5V Current (5v): Weight: 1.5gram without antenna Center distance of mounting holes: 16mmx16mm 20mmx20mm 25.5mmx25.5mm Due to different batches, the appearance, color and printed words of the product , which will not affect the use. Colour:Black Material:PCB Package Contents: 1 x Kit Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.