[Heathkit] DX-20 T/R Switching?

[Curt]

I built a relay box to switch antenna between transmit and receive for a 
recently acquired DX-40.
Contemplating acquiring a DX-20, was surprised to notice it has no provision 
for providing switched power
for a relay.  Never having owned any Heathkit transmitter in my old Novice 
days, am wondering how folks
performed T/R switching with the DX-20 or AT-1?

73, Curt KB5JO