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It looks like it is a simple AB selector for one amp and two sets of speakers, but only for adding a speaker zone and not for AB comparing since there is no way to balance the outputs.
I suppose you could use it backwards and have two amps connected to one set of speakers using a wye connector from your preamp to two basic power amps, but as others have said, again you have no gain control. If your amps offer input gain controls then you could make it work for AB comparing the two amps.
^^^ Almost everything one has to know in electronics!
(well, that and you should also probably know that E is often used to represent voltage in lieu of V.