The three touch sensors are wired through a resistor ladder to a single sensor input. Using three different resistor values, the 8 combinations of ON and OFF become 8 distinct input levels, and the robot software can decode the input into three separate binary input values.

modified electric plate

The upper plate has been cut in three places so that the conductor running along that edge is broken into 4 separate segments.

The lower plate has been further modified by removing the "tube" material in 3 places.

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