MOTM

An additional note: unlike a VCA, the RM output does not include either of
the 2 input frequencies, only their sum and difference.  And this is where
Paul's excellent RM design gives us extra functionality: the UNBAL control
allows one to "bleed" the original Y-IN input into the RM output.  Also, you
can also remove the DC offset from either or both inputs by setting the
switches to AC accordingly.

George (wondering what features the 110-replacement RM will have)