Within 2 days no more scratching in the walls.

I've had a mouse problem in this house for 20 years. I'd been dealing with it with spring traps, which would reduce the activity but I'd still hear them in the walls. Tried a ‘Coleman ultra-sonic’ pest repeller, but frequency is low enough I can hear it, drives me nuts. So I stayed away from sound based repellers for a long time. Last week I decided to look into the ‘Riddex’ units advertised on TV, found your web site, and decided yours is the better product. Bought 2 Ultimate ATs, plugged them in, within 2 days no more scratching in the walls. I just ordered another 2 for the basement, and an outdoor one [the Guardian] which I'll use to try to keep the mice out of my cars.