It was pretty much the set that really started many people on the path to having robotics as their major hobby. and introduced mindstorms. The set was a turning point and vastly lowered the barrier to entry.
It is set to be replaced by the NXT in Q3/4 2006.
There were four releases of the RIS (1.0(a and b), 2.0 and 3.0), each with slightly revised software and different bricks, multiplied by the locale/language specific versions of these. The earlier 1.0 set (of which there were actually two versions anyway) was sought after for its inclusion of a 9v power socket on the RCX brick itself, which was subsequently removed. The 1.0 version shipped with a serial port based tower.
The 2.0 Version shipped with a USB tower, revised firmware on the RCX brick and updated software, although the software updates were available for download separately for free on the Lego mindstorms website.
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