Editing 1129: Cell Number

{{comic
| number    = 1129
| date      = November 2, 2012
| title     = Cell Number
| image     = cell number.png
| imagesize = 
| titletext = There's also a +1 sometimes, which is there to keep everyone on their toes. In the future, people who got to pick cool numbers by signing up for Google Voice early will be revered as wizards.
}}

==Explanation==
This comic references the pattern for US telephone numbers, which are ten digits in length.  Unlike in other countries, there is no way to determine (simply by looking at the number) whether that number is a land-line or mobile customer.  In either case, the first three digits are referred to as the Area Code.  Prior to the proliferation of cell/mobile/handy phones, geographic regions were assigned a specific area code, and the middle digit was originally always 0 or 1 to allow mechanical dialing circuits to identify the sequence as an area code or not.  The next three digits are the exchange number (the middle digit being always 2 or higher), and the final four digits are typically random, though business customers frequently could pay a premium for a specific number (if available,) either to spell a brief slogan, or for easy memorization.

According to the {{w|North American Numbering Plan}}, currently the first 3 digits (area code) can be: [2-9][0-9][0-9], the next 3 digits (Exchange) and can be [2-9][0-9][0-9], and the final 4 digits (Subscriber Number) can be [0-9][0-9][0-9][0-9].  There are [http://www.nanpa.com/area_codes/index.html some rules] for area code exceptions or reserved numbers though.  Specifically, X11 codes are not valid as area codes(e.g. 411, 911, etc...) and Xyy (repeated last 2 digits) codes are reserved for special use area codes (e.g. toll-free/freephone 800, 888, etc..)

The prevalence of digitally controlled dialing allowed the restrictions on digits in area codes and exchanges to be relaxed, suddenly making many new area codes and exchanges available.

Late in 2003, US telephone service providers were required to support "number portability", meaning that customers could theoretically take their cell phone number with them to a new provider, even when moving to a new geographic location.  However, in the early days at least, this wasn't always very easy to do.

Similarly, when purchasing a cell phone, customers could frequently pick from any exchange (middle 3 digits) that a carrier provided service to, and any available four-digit number within that exchange.  People would do this to pick an exchange close to their land-line friends and relatives (to avoid long-distance charges) or for "vanity numbers" much like businesses used to be able to select.

As a result, the comic's illustration reflects this structure: the first three digits (Area Code) show the geographic region one was in prior 2005 (after which time, number portability was much easier) and the remaining digits are in effect entirely random.

{{w|Google Voice}} is an alternate {{w|voice over IP}} service. Users can choose a new phone number upon signing up in any available area code and/or exchange and forward calls to any other number.

==Transcript==
:[10 boxes for 10 digits of a U.S. phone number. The first three are grouped by parentheses. A hyphen separates the second set of three and the last four.]
:[Label titled "Your seven random digits" pointing at seven empty boxes.]
:[Label titled "Where you lived in 2005" pointing at three empty boxes preceding the seven.]
:Structure of a US cell phone number.

{{comic discussion}}