I can tell you landlines VERY seldom display the wrong information, but if you want to test yours, call the NON emergency dispatch number for your jurisdiction and ask first. That makes sense, doesn't it? Dispatchers don't want you calling and testing your phone while they are working a major event, and may have certain policies on testing. They deal with a lot of stress, give them a break if they got a little cranky because you tested your phone and didn't check first to see if it was okay.