Vehicle turrets and weapons

Can anyone explain to me how they work, things like the ballista, or the turrets I’ve seen on some armoured cars?

You need a electronic control unit to use them I think. At lesst for cars.

Turret firing mode means whether it’ll shoot once(semi-auto) per turn or multiple times(auto).

Turret targeting mode means whether it’ll shoot automatically(auto) or you have to manually fire it(manual).