germany has an open telephone numbering plan. there used to be no fixed lengths for either area codes or subscriber telephone numbers, meaning that some subscriber numbers may be as short as two digits. as a result, dialing sequences are generally of a variable length, except for some non-geographic area codes for which subscriber numbers use a fixed-length format. it is not possible to determine unambiguously the end of a phone number from a prefix or the digits already dialed. this feature allows the extension of the length of phone numbers without revoking or changing existing numbers. cell phone numbers in germany are not given geographic area codes but non-geographic codes. thus they can easily be told apart from other numbers.