= GSM =
GSM (Global System for Mobile Communications, originally Group Spécial Mobile), is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe protocols for second generation (2G) digital cellular networks used by mobile phones. 

== AT command set for GSM Mobile Equipment ==
Adapted from http://www.etsi.org/deliver/etsi_gts/07/0707/05.00.00_60/gsmts_0707v050000p.pdf

From 5.6 in page 15

||Command || Purpose || Mandatory ||
||ATZ     || Sets all parameters to their defaults || true ||
||ATI     || Requests manufacturer specific information || false ||
||AT+GMI     || Requests manufacturer identification || true ||
||AT+GMM     || Requests model identification || true ||
||AT+GMR     || Requests revision identification || true ||
||AT+GSN     || Requests serial number  || false ||