function check_phone ( Phone , Digits ) {

    // strip off non numeric characters
    P = String(Phone).replace(/[^0-9]/g, "");

    // ensure the phone number contains the correct number of digits
    if( P.length != Digits ) {
        alert( "Please enter a valid " + Digits + " digit phone number." );
        return false;
    }
    return true;
}