DALI Lighting Control
KNX integration with the KNX- DALI gateway opens a whole new world of possibilities. One of the most recent of these developments is the Automatic Emergency Light Testing.
DALI is an open standard, developed and maintained by the Dali action group http://www.dali-ag.org
Not being exclusively owned by a single company or group means that there is an extensive range of good, competitively priced products out there in the market place.
DALI is a robust protocol based on the "Manchester encoding" system. The two core bus wires can be configured in any topology as long as it is not a closed loop. Polarity of the cable can also be reversed without detriment to the interpretation of the signal. The DALI signal also has a high signal to noise ratio (SNR) consequently the signal has a high tolerance to external interference before sign degradation.;
Reference:-
For more information about DALI and its history please see the links below.
http://www.dali-ag.org/c/manual_gb.pdf
http://en.wikipedia.org/wiki/Digital_Addressable_Lighting_Interface