[Elecraft] Interlocking two K3

[irdixon+lists]

Hi All
I don't like re-inventing the wheel, so I'm looking for a design to 
copy!
I'm looking for a circuit to interlock two K3 so they cannot transmit 
simultaneously.  I am aware of the simple connection cross linking the 
PTT out and Inbibit input on the 15 pin connector.  That does not meet 
our needs as when both try to transmit - both are inhibited !!

TIA
Roger - G4BVY