more than 1 radio with Sigtronics Sport 200 S Two Place Intercom

Hello,
I want to have 2 radios hooked to my Sport 200 S a Valcom 760 and a
Sporty's handheld that is mounted to the panel. I want to be able to
monitor both radios and switch between the 2 for transmit. Is it as
simple as wiring both radios to the same audio inputs in the 200 S and
add a switch to the mic key? Is there somewhere on the internet that
shows how someone has already done this?
thanks