{TAIL ~ The squarer output} is applied to a summing amplifier, which removes {HEAD ~ the multiplex frequency}, and which provides a dc signal which is applied to a comparator 
{ TAIL ~ The squarer output } is applied to a summing amplifier , which removes { HEAD ~ the multiplex frequency } , and which provides a dc signal which is applied to a comparator
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH