From the apertusº Open Source Cinema project:

The AXIOM photonSDI hardware is an extension board for the apertusº AXIOM Beta open source camera that adds 6G SDI connectivity to its features.

The board has two independent 6G SDI outputs that can both output the same image, different images, or be used in a dual 6G configuration that allows the transmission of 4k video material at 60 frames per second. Additionally the board contains a 6G SDI input for synchronisation and blending and a legacy synchronization input.