In article .com,
writes
If cutting the vario when the mic is keyed is the objective, could the
PTT be wired to cause a relay to open the vario speaker circuit? Then
the technique could be used with any radio?

I had to do something like that with my last glider.

If the A/H was running when I used the radio, nobody could hear anything
except hash from the inverter. So I arranged a relay switched by the PTT
to cut off the inverter. That sorted it.
After all, it doesn't take more than a second to announce you are going
into cloud.
--
Mike Lindsay