Mouseblocker electronic repeler?

dirty white boy said
couple good black snakes will keep the mice and other small critters away,..just need a good hart so it wont stop when one startles you!!!

Have black snakes, but the mice are still a problem. Can't imagine what it would be like without the snakes. Makes me mad when someone kills one.
Thinking maybe cats may be more of a deterrent, but they can be troublesome too.