Cablecast supports the control of several DSK units that add the ability to key over any content that passes through it. The built in video overlay feature on SX video servers is only able to key over content that comes from the video server. Adding a DSK unit allows you to key over live and all other programming.
The following is a list of controlled units as of 5.4.x. They are in order from least to most expensive.
ChyTV, ChyTV Plus, and ChyTV SDI models
ChannelBrander Analog, ChannelBrander SD-SDI, ChannelBrander HD models.