From the factory the box is configured to control camera IDs 1-8. When input 1-8 is closed to GND, the red tally flag for camera 1-8 respectively will be set on the SDI output from the box. Likewise input 9-16 (on the same DB25 connector) will result in green tally (preview) being set on the SDI output. If you want tally control of camera IDs other than 1-8 or if you want just red tally for camera 1-16 for instance, you simply configure the inputs in the web interface.
The SDI input should be connected to your source for the camera return feed. This would typically be a program output and possibly enriched with CCU data via either an ATEM switcher, the SKAARHOJ RCP, or the Blackmagic Arduino Shield.
The SDI Tally box passes through all CCU information and only overrides Tally information. Camera Support The Blackmagic 3G-SDI Arduino Shield supports the following formats using SDI Level B: 720p50, 720p59.94, 720p60, 1080i50, 1080i59.94, 1080i60, 1080p23.98, 1080p24, 1080p25, 1080p29.97, 1080p30, 1080p50 (output only), 1080p59.94 (output only) and 1080p60 (output only), but the camera doesn´t have to be running the same video format as the program input, so you can use cameras in Ultra HD while the camera protocol is sent over HD signal to the camera.
Please Note: SKAARHOJ Controllers with GPI inputs accept open collector relay outputs (pulled to GND). The default HD15 tally connector on the TriCaster TC1 does not provide a direct working signal to the SDI-GPI Link. Converting the 5V potential to GND is needed.