WAGS2 is designed to use a four channel Blackmagic Design Decklink card. If you only need to output in resolutions up to 1080p, we recommend the Decklink Duo 2.
WAGS2 is a two channel system, but uses three output channels and one input channel on the Decklink card.
Two output channels are designated for key and fill signals (of the WAGS2 overlay channel) for downstream key. This can be changed to enable internal keying. The third output channel is for full screen output. The last channel is used as an input for external sources.
If you only wish to use WAGS2 as a standalone playout system and do not need the ability to key graphics over external video, a less expensive Decklink card should suffice.
More information about Blackmagic Design Decklink cards can be found on their website: www.blackmagicdesign.com.