{TAIL ~ The detectors} are positioned to provide a first pair of output signals in phase quadrature and representative of {HEAD ~ the interference fringe pattern inpinging thereon} 
{ TAIL ~ The detectors } are positioned to provide a first pair of output signals in phase quadrature and representative of { HEAD ~ the interference fringe pattern inpinging thereon }
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD