deletions | additions       diff --git a/EM Switch Activation.tex b/EM Switch Activation.tex  index 2662676..94b7c28 100644  --- a/EM Switch Activation.tex  +++ b/EM Switch Activation.tex 
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The bars had cut grooves that interact with the switches and feet on the bottom of the test units,  sitting in the tray; see Section \ref{sec:tray} for details.  The spars had two purposes: one, to support the plate on the rails on which it slid,  and two, to provide attachment points for the servomotors that move the plate back and forth to turn on the lights. Two rails, constructed of aluminium angle bracket,   were mounted on opposite sides of the frame to support the plate.   The outermost spars each had small pieces of aluminium angle bracket attached at front and back to allow the plate to slide.  The rails were lubricated with PTFE to reduce friction.