Wireless service providers reveal coverage--good and bad.

IF YOU USE A MOBILE PHONE, you know dead zones and areas with poor signals are common. Prospective mobile service customers want to know where those weak areas are before they sign on the dotted line. Although most wireless service providers offer network coverage maps, they don't offer much detail--usually just large blocks of color to indicate what cities have service.

Now, Cingular and T-Mobile are providing maps that give detailed information on mobile phone reception, right down to specific streets. For example, prospective customers can go into a T-Mobile store and enter an address to get detailed, color-coded maps showing signal strength (strong, adequate, weak, or nonexistent). For now, T-Mobile considers the maps a tool for its sales people, so customers can only see them by going into a T-Mobile store.