[Kenwood] Amplifier Keying from various transceivers

[Mark Nace]

I have been keying my TL-922 with my Knwd 850 for over 15 years, and of course its relay contacts can handle the 922 coil current. I want to start also using another brand (756pro) a little and know its relay cant hack it. I could buy the ameritron interface, but is there a simple free schematic out there for building a solid state interface from scratch that would cost less than 50 bucks?  Any help much appreciated. 
73
Mark
N5KAE