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