Can someone please help me understand this logic circuit from the Sony SQD-2020, service manual attached. I marked point a1 and point a2 as I'm considering them to be different nodal voltages, although the manual states they are the same, circled as |Lf - Rf|. I did conclude a1 = |c| - |f| and a2 = |f| - |c| as c and f are the output signals coming straight from the Modified SQ Decoder into the full wave rectfiers. Then, a1 and a2 go to a negative rectifier which I assume will be the sum of the negative semicycles of a1 and a2, resulting in what I called at, whice has nothing above 0. Am I missing something that would make a1 and a2 the same thus |Lf - Rf|?
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