Turboprops
Quite a lot of the turbo-props you come across utilise an emergency brake system that can be as simple as applying the park brake, which can use a seperate accumulator of fluid.
Generally speaking though your alternative braking system is manually selected.
Alternate is probably an unfortunate choice of wording 'cos if my memory serves me right the 757 has an automatically switched alternate brakes system with a selectable reserve brake function if it all goes wrong.