iOS 5.1 on iPhone 4s status bar icons

Ever since updating my iPhone 4s to the new iOS 5.1, my status bar icons tend to change. Sometimes there's nothing at all showing. Sometimes it shows 3G. Sometimes it now shows 4G. At other times, it displays a telephone with an arrow facing right. I've read various reports about the 4G icon's meaning but what is the telephone icon trying to convey?

Thanks!