deletions | additions       diff --git a/electromech extrinsic.tex b/electromech extrinsic.tex  index 7994f5f..fec9a7a 100644  --- a/electromech extrinsic.tex  +++ b/electromech extrinsic.tex 
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The only extrinsic problem of note that had to be considered at the conceptual design stage arose from the circuits subsystem.  The design of the sensors for the device required first that the sensor be in close proximity to the test units,  and second that the each test unit be optically isolated from all other units.  Together, these requirements led to the design of the second major electromechanical unit in the final product.