Editing Hayes AT command set (section)

== GSM ==
The ETSI GSM 07.07 (3GPP TS 27.007) specifies AT style commands for controlling a [[Groupe Spécial Mobile|GSM]] phone or modem. The ETSI GSM 07.05 (3GPP TS 27.005) specifies AT style commands for managing the [[Short Message Service]] (SMS) feature of GSM.

Examples of GSM commands:<ref name="sonyericsson_65054">{{cite web|title=Developers guidelines June 2010 AT commands for Sony Ericsson phones|url=http://developer.sonyericsson.com/wportal/devworld/article/technology-more-atcommands?cc=gb&lc=en|url-status=dead|archive-url=https://web.archive.org/web/20110929223402/http://developer.sonyericsson.com/wportal/devworld/article/technology-more-atcommands?cc=gb&lc=en|archive-date=2011-09-29}} 090505 developer.sonyericsson.com</ref><ref name="m2m-platforms_com_UC864E_guide">{{cite web|title=UC864-E Software User Guide|url=http://www.m2m-platforms.com/data/1vv0300767_UC864-E_Software_User_Guide_Final_DRAFT.pdf|url-status=dead|archive-url=https://web.archive.org/web/20110714011104/http://www.m2m-platforms.com/data/1vv0300767_UC864-E_Software_User_Guide_Final_DRAFT.pdf|archive-date=2011-07-14}} 090505 m2m-platforms.com</ref>
{| class="wikitable"
! Command !! Description
|-
| AT+CPIN=1234 || Enter [[Personal identification number|PIN code]]
|-
| AT+CPWD="SC","old","new" || Change PIN code from 'old' to 'new'
|-
| AT+CLCK="SC",0,"1234" || Remove PIN code
|-
| AT&V || Status
|-
| ATI || Status (Manufacturer, Model, Revision, [[International Mobile Equipment Identity|IMEI]], capabilities)
|-
| AT+COPS=? || List available networks 0-Unknown/2-Current/3-Forbidden, Longname, Shortname, Numerical-ID, "AcT"
|-
| AT+CSQ || Get signal strength. Answer: +CSQ: <[[Received signal strength indication|rssi]] (more=better)>, <[[Bit error ratio|ber]], less=better>
|-
| ATD*99# || Dial access point
|-
| AT+CGDCONT=1,"IP","access.point.name" || Defines [[GPRS Core Network#PDP context|PDP context]]<!--P192--><ref name="sonyericsson_65054" />
|}

GSM/3G modems typically support the ETSI GSM 07.07/3GPP TS 27.007 AT command set extensions, although how many commands are implemented varies.

Most USB modem vendors, such as Huawei, Sierra Wireless, Option, have also defined proprietary extensions for radio mode selection (GSM/3G preference) or similar. Some recent high speed modems provide a virtual Ethernet interface instead of using a [[Point-to-Point Protocol]] (PPP) for the data connection because of performance reasons (PPP connection is only used between the computer and the modem, not over network). The set-up requires vendor-specific AT command extensions. Sometimes the specifications for these extensions are openly available, other times the vendor requires an NDA for access to these.<ref name="dan_williams_blog_revolver">{{cite web|title=Dan Williams' blog – That's when I reach for my revolver…|date=March 20, 2009 |url=http://blogs.gnome.org/dcbw/2009/03/20/thats-when-i-reach-for-my-revolver/}}</ref>