Topband: 4 Direction Reversible Beverages Remote Control via Coax Feedline

[k2waltk]

Hey all,
 
I was wondering if anyone has built  a circuit to control the switching of a
pair of two-wire reversible beverages, using only the coaxial feed to carry
the control
signals.  The usual design calls for 3 DPDT relays.  One relay is used for
beverage selection and one each for direction and unused port termination.
In other words, one relay for the NE/SW directions, another relay for the
NW/SE directions and the third relay is used to select between the two
reversible beverages.  The truth table is straight forward, but the
circuitry to accomplish this is beyond this old, feeble brain addled with
advanced CRS.  I can't figure out the circuitry (diode matrix?) to route the
control signals to the 3 relays.  I understand how to isolate DC from RF,
through the bias-T method and I've seen designs using positive, negative and
AC to accomplish 'generic' remote antenna switching.  Maybe I can use a
similar method to build the control switch back at the shack and the remote
relay box.  Any of your suggestions, diagrams or references would be greatly
appreciated.
 
                                    73 de Walt - K2WK
                                    Gordonsville, VA