Normally, the demultiplexer and the multiplexer are controlled by the tone switching logic ciruit so as to alternately couple, at the multiplex frequency, the mixed signal to {HEAD ~ the inputs} of {TAIL ~ the first and second filters}, and the outputs thereof to the squarer 
of
Normally , the demultiplexer and the multiplexer are controlled by the tone switching logic ciruit so as to alternately couple , at the multiplex frequency , the mixed signal to { HEAD ~ the inputs } of { TAIL ~ the first and second filters } , and the outputs thereof to the squarer
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 REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH