DSI Lighting Control
DSI was one of the first proprietary protocols to digitally control electrical ballasts. Like 1-10v it is very simple and easy to implement. As the predecessor to DALI, individual ballasts are not uniquely addressable like DALI. Each run of lights is controlled as a single entity.
Each switching zone (run of joined DSI ballasts) then requires a control cable, this means the overall topology is similar to 1-10v i.e. a star arrangement.
DSI has the same advantages as 1-10v: simplicity of deployment and troubleshooting. It also has similar disadvantages of large DSI installations requiring complex and expensive runs of multi-core cable.
DSI integration with KNX is achieved though a gateway device. Although less flexible than DALI, the advantage of DSI over DALI are that the ballasts are not addressable. When a ballast fails, no programming is required to replace the ballast.
Reference:-
http://en.wikipedia.org/wiki/Digital_Signal_Interface