The switching circuits are chosen such that defects causing the electrical switching circuit to short circuit do not affect the electromechanical switching circuit and defects causing the electromechanical switching circuit to {HEAD ~ short circuit} do not affect {TAIL ~ the electrical switching circuit} 
The switching circuits are chosen such that defects causing the electrical switching circuit to short circuit do not affect the electromechanical switching circuit and defects causing the electromechanical switching circuit to { HEAD ~ short circuit } do not affect { TAIL ~ the electrical switching circuit }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL