Magneto starting

Some aircraft with two magnetos only start on one magneto.
How is the second magneto removed from the circuit? Is it
done at the ignition switch?

Thx

It depends on the airplane. Often, the ignition switch grounds out the magneto that doesn't have the impulse coupling when you turn the switch to START. In others, like my plane used to have, the mag switch is distinct from the starter, so I put it on L before pushing the starter switch.

My ignition is setup like in Ron's plane--the mags are controlled separately from the starter but in my case the starting Mag (the left one) is a retard breaker with a starter vibrator (SlickStart) vs an impulse coupler.

Thanks for the help folks