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 the inputs of the first and second filters, and {HEAD ~ the outputs} thereof to {TAIL ~ the squarer} 
to
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 the inputs of the first and second filters , and { HEAD ~ the outputs } thereof to { TAIL ~ 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL