What Is FDN Mode In Mobile Phones And What Is Its Function?

FDN stands for 'fixed dialling mode' - the setting on a mobile phone which prevents the dialling of a number that does not match the data on your SIM card. It is also used as a security measure when you are away from your phone; in particular when you do not want someone to use it to make an unauthorized call - unless the actual phone number is located in your SIM card, the user will be unable to make the call.

If you need to find out the default password on your phone to enable FDN mode, all you need to do is press either 0000 or 1234, depending on your phone.

FDN, in essence, only allows outgoing calls to those numbers listed or to numbers with certain prefixes. A notable exception is when the phone is in emergency mode - vital in an urgent situation, thus calls to emergency numbers such as 112, 911, 999 and the like are exempt (in most cases typically require no SIM or even an active network). Incoming calls are not affected whatsoever by FDN mode.

Not all SIM cards support the FDN feature. To enable FDN on your phone, it is sometimes necessary to enter your PIN2 number beforehand - a security number individual to each SIM card which is initially provided by the network operator (please check with your service operator if you are in any doubt). This is in place as a security measure, preventing unauthorised users from moving, editing or disabling the FDN list. The PIN2 code is completely different to the main PIN1 number which, when set, can lock and unlock the SIM card and applies to both inbound and outbound calls.

Fdn is fixed dialling numbers,: A list of numbers which you can create in your sim card phone book called fdn list it is the same as your phone book. When fdn is activated only the numbers in the fdn list can be called. It is a way of locking down the phone for example if I have this number: 123456 in the fdn list on its own and I want to call a different number like 654321 it will block the number. Only numbers in the fdn list can be called except 112 or 999 calls. I use fdn to enter prefixes like 01302, doncaster number, 01262, bridlington number etc... So I don't accidentally call premium numbers. Here is how mine is set up:
I have the following numbers in my fdn list: 01, 02, 03, 071, 072, 073, 074, 075, 077, 079,
because I have the first 3 numbers of prefixes only phone numbers with these prefixes can be dialled this will prevent me from accidentally calling an 0845 number which is expensive as 084 is not in the fdn list unless you add it. Thats how mine is used. If you have children and want to give them a phone with fdn function, you can protect them by adding parents or home phone numbers to the fdn list in full like 12345 676767 etc... Only those calls can be made from the phone which will stop the child from calling different numbers. This also applies to text messages although calls and texts received are still connected but cannot be sent from the phone. Its like phone parental control. To activate fdn you need a pin2 code, this is usually the same as the default pin. If you are with 02 the default pin and pin2 are: 5555. If 3 wrong pin2 codes are entered the phone will require a PUK2 code which can be obtained by your service provider but you must use fdn with caution as if you block the pin2 not all service providers have a puk2 code available, as a result you will have to buy a new sim. Virgin mobile and vodafone definately support fdn. You require a phone with fdn functions such as a samsung model. I use samsung d840, I have owned a samsung j600 which also has the capabilities.
I hope this has helped you a bit on fdn. Its just a parental control type thing for parents and businesses to prevent unauthorized numbers being used.

Thanks

The term FDN stands for fixed dialing number. This is a feature that is provided by your SIM card. Some SIM cards don't allow or support this functionality.It is used to restrict your out going calls to a limited set of numbers.

In this mode you can only dial the number from your mobile phone that is added to your phone book. You are not allowed to call to any other number from this SIM card.
This feature is normally used to secure your phone from unwanted or unauthorized use. Some times you are away from your mobile phone, and some one tries to dial a number with out your permission. If that number is not in your phone book then it can not be dialed. It saves your SIM balance from rum away unnecessarily by anyone that is not allowed to use it.

To make this feature enabled, you must enter your PIN2. The PIN2 is actually the personal identification number that is provided by your network operator and it is unique for each SIM card. You can change it accordingly as you want. No body can change your phone book of your mobile phone with out entering this personal identification number.

I want to disable fdn mode

Every handset can support FDN? Or it is just influenced by SIM card?  What's the factor there is FDN menu or not in handset display?how about FDN in CDMA, is it has same behaviour as GSM?need your help, thanks