More Must-Know Cell Phone Acronyms

My recent post about must-know cell phone acronyms got a huge response—sounds like a lot of you are interested in finding out what all those confusing abbreviations mean. In fact, I got a comment from reader Allronix, a cell phone tech support rep who had a few more definitions he though might be helpful. Here they are (along with a few minor edits and comments)—and many thanks, Allronix, for sending these in.

• ESN (Electronic Serial Number) or IMSI (International Mobile Equipment Identity): Think of this as the identifier for the phone. Like fingerprints, each one's unique. This is how cell towers know to ring to your phone when someone calls your number. [Note: ESNs are used for CDMA phones, while IMSI numbers are for GSM handsets. Also of note: according to Phone Scoop, cell phone makers began running out of unique 32-bit ESNs last year (only 4 billion are available); the industry has since adopted a new standard, the 56-bit MEID (Mobile Equipment Identity), which will yield 16 million times as many numbers as ESNs ever could.]
• MIN (Mobile Identity Number): When people began "porting" their numbers from one carrier to another, the MIN was introduced so that the system knows the number belongs to it. If you've ported your number to another carrier, your new MIN will not be the same as your phone number. If you've never taken your phone from one carrier to another, your MIN will be the same as your phone number most, but not all, of the time.
• MDN (Mobile Directory Number): Fancy way of saying "your phone number."
• SID (System ID): About the size of an area code in most places, it's what's programmed in the phone to identify a certain area as "home." Phones, if they pick up something other then the SID programmed into them will show "Roaming." If you are roaming in your home area, please let your carrier know.
• WAP (Wireless Access Protocol): Basically, how your phone connects to the Internet. It's more limited currently then the standard HTTP protocol, so pages on your phone will not display the same way they do on your home PC. [Note: Just about every current phone on the market comes with a WAP browser, although more advanced models may come with a full HTML browser.]
• E911 (Enhanced 911): This is the reason you can't dig out your old brick CDMA phone from 1999 and slap it onto your account. Every phone that your carrier activates has to employ technology that allows emergency personnel to find you if you call 911. [Note: E911-compliant technology (now mandated by the FCC) differs from carrier to carrier. CDMA carriers Sprint and Verizon Wireless use GPS or A-GPS (GPS assisted by cellular positioning), which means you'll need a newer phone with built-in GPS technology. GSM carriers AT&T and T-Mobile use a technology called "time difference of arrival", or TDOA, which calculates a caller's location according to how long it takes for the signal to reach three or more nearby cell towers. TDOA technology will work with any GSM phone—no need for a special chip.]