AT commands also called as Attention Commands or Hayes Command
AT commands can be used to collect information from the modem device or the network and can help you troubleshoot modem specific issues. Below are the list of AT commands that most of the Modems uses.

AT Commands	Meaning
AT+CSCA="+651234567"	Set Message Center Number
AT+CGMI	Get the name of manufacturer
AT+GMI	Get the ID of manufacturer
AT+GMM	Get the Model information
AT+CGSN	Get IMEI number (International Mobile Equipment Identity)
AT+CGMR	Get software version
AT+CIMI	Get IMSI number (International Mobile Subscriber Identity)
AT+CNUM	MSISDN
AT+CPAS	Get mobile phone activity status
AT+CREG	Get mobile network registration status
AT+CSQ	Get radio signal strength
AT+CBC	Get battery charge level and battery charging status
ATD, ATA, etc	Establish a data connection or voice connection to a remote modem
ATD, ATA, AT+F*	Send and receive fax
AT+CMGS, AT+CMSS	Send SMS messages
AT+CMGR, AT+CMGL	Read SMS messages
AT+CMGW	Write SMS messages
AT+CMGD	Delete SMS messages
AT+CNMI	Obtain notifications of newly received SMS messages
AT+CPBR	Read phonebook entries
AT+CPBW	Write phonebook entries
AT+CPBF	Search phonebook entries
AT+CLCK	Opening or closing facility locks
AT+CPWD	Changing passwords
AT+CMEE=n	Enable certain error messages
	n= 0 disable +CME ERROR: result code and use ERROR instead.
	n= 1 enable +CME ERROR: result code and use numeric values.
	N= 2 enable +CME ERROR: result code and use verbose values.
AT+COPS=, ,	Change the GSM network  is used to select whether the selection is done automatically by the ME or is forced by this command tooperator given in the format and may be:
	= 0 automatic ( field is ignored).
	= 1 manual.
	= 2 deregister from network.
	= 3 set only .
	= 4 manual / automatic (if manual selection fails, automatic mode is entered).
	:
	= 0 long alphanumeric (default value).
	= 1 short format alphanumeric .
	= 2 numeric .
	string type given in format ; this field may be up to 16 character long for long alphanumeric format, up to 8 characters for short alphanumeric format and 5 characters long for numeric format MCC/MNC codes)
AT+CBST	Change bearer service type
AT+CRLP	Change/configure radio link protocol parameters
AT+CPMS	Storage of SMS messages
AT+CSAS	Save configurations of the GSM/GPRS modem
AT+CRES	Settings related to SMS messaging such as the SMS center address
AT+CMGF=1	Instruct the GSM / GPRS modem to operate in SMS text mode
AT+CMGL="ALL"	List all the messages
AT+CNMA	New message acknowledgement

Check out  this post : "HOW TOs with AT Command"

List of applications for making Free Calls

Here we are in the era where
World has become a "Global Village"
And its good that we have a communication access to connect to any part of the world, and the best part is
when it is free.
Yes, there are services around the internet to call anyone just for free. You can make free calls. You  just need an internet connection, a computer, speakers/headphone and a mic.
Though Paid one are always there with some extra sophisticated services.
Below is the table that would give an overview.

	Receive Calls	SMS	Voicemail	Mobile	OS Supported
JAJAH	YES	YES	NO	YES	Web-based
ooVoo	YES	YES	NO	NO	Win, Mac
Skype	YES	YES	YES	YES	Win, Mac, Linux
iCall	YES	NO	YES	YES	Win
VoxOx	YES	YES	YES	NO	Win, Mac
Vyke	NO	YES	NO	YES	Web-based
Yahoo! Voice	YES	YES	YES	YES	Web-based, Win, Mac
FriendCaller	NO	NO	NO	YES	Web-based
vBuzzer	YES	YES	YES	YES	Web-based, Win, Mac
VoipBuster	NO	YES	NO	YES	Win
MOBIVOX	YES	YES	NO	NO	Web-based
Line2	YES	NO	YES	YES	Mobile (iPhone)
MagicJack	YES	NO	YES	NO	Win, Mac
Vonage	YES	NO	YES	YES	N/A
Google Voice	YES	YES	YES	YES	Web-based
Tru	YES	YES	YES	YES	Mobile
Fring	YES	NO	NO	YES	Mobile
EvaPhone	NO	NO	NO	NO	Web-based
PC-Telephone	YES	NO	YES	NO	Win
Rebtel	YES	YES	NO	YES	N/A
MyCallingBox	NO	NO	NO	NO	Web-based
Miglu	NO	YES	NO	NO	Web-based
Voxtopia	YES	NO	YES	YES	Mobile
PokeTalk	NO	YES	NO	NO	Web-based
WebPhone	NO	NO	NO	NO	Win
GMail	YES	NO	NO	NO	Web-based
My-B-line	NO	NO	NO	NO	Windows
PowerVoip	NO	YES	NO	YES	Win, Mac, Linux, Web-based
uVOIPit	NO	NO	NO	NO	Windows

Save your Battery life

You must be worrying about the drainage of your mobile battery and must be thinking..what is wrong with this battery and why it does not last longer.
 I can provide few simple extra tricks or rather Tips to save your mobile battery
 Here they are:

1. First would be "Switching off your Mobile" ..LOL
 This would definitely save your battery. Dont take this in other way, what I meant is, switch off your mobile when you know that you are not going to make / answer any call or you dont want to use your mobile. When you know you will be in "No network" coverage area, there is no point keeping to mobile phone ON. Your phone will continue to search for network and loose all of its power in searching a Network coverage.


2. Do not Vibrate: 
When someone calls to you, your phone will Ring as well as Vibrate. Here your Phone's Speaker as well as the Phones Vibrating motor will consume the battery together. So to save some battery life, you can turn off the vibration mode of the mobile and if possible keeping the Ring Volume low so that you can listen the ring if someone calls.

3.  Turn off the Bluetooth and Wifi: 
If your phone supports Bluetooth or Wifi or Both, switch them Off. If any of these services are running that will loose huge amount of battery power. There are other features like GPS, Infrared (though Obsolete :) ) should also be turned off to save power.

4. If the mobile phone support Brightness feature, keep it too the lowest possible. Because your screen is also a huge consumer of battery.

5. If you have Screen saver or animated image as a wallpaper, change it some dark colored image. Animated background can also drain your battery faster

6. Remember the Golden Rule: Full Charge and Full Discharge
Dont put your mobile on charging when its having some power enough to last for next few hours (do this when your charger is handy)
And when it is charging let it charge it too full.
NOTE: Avoid full discharging of a lithium-ion battery
Unlike Ni-Cd batteries, lithium-ion batteries' life is shortened when you fully discharge them. Instead, charge them when the battery meter shows one bar left. Lithium-ion batteries, like most rechargeable batteries, have a set number of charges in them.

7. To make your battery last longer, always keep it in cool place.

8. And Remember, do not use faulty Chargers, if the charger is faulty or broken, it may lead to make your battery faulty as well.


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Apple Iphone secret key codes

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Now this seems to be new..

Apple iPhone Secrets/ Apple iPhone hacks

Below are few Apple iPhone Codes that  are new to me.
If you have something new or extra to add feel free to add in comments.

*3001#12345#* and press Call key	Enter Field Mode
*#06#	Displays your IMEI
*777# and press Call	Account balance for prepaid iPhone
*225# and press Call.	Bill Balance. (Postpaid only)
*#33# and press Call	Check for call control bars
*#67# and press Call.	Check the number for call forwarding when the iPhone is busy
*#62# and press Call.	Check the number for call forwarding if no service is available
*#61# and press Call.	Check the number for unanswered calls
*#43# and press Call.	Determine if call waiting is enabled.
*#76# and press Call.	Check whether the connected line presentation is enabled or not
*#30# and press Call.	Calling line presentation check
*#21# and press Call.	Setting interrogation for call forwards
*646# and press Call.	Check minutes. (Postpaid only)
*225# and press Call.	Bill Balance. (Postpaid only)