Software Version
Type *#0000# For checking the phones software (SW) - called firmware revision information.
e.g. : Version V. 4.51 (26-03-98) will display V 04.51 26-03-98 NSE-1
first line: The Software Version
second line: The Date of the SW release.
third line: Compression type
Please go to the Nokia website for latest software release information. www.nokia.com

Type *#746025625# [*#sim0clock#] to check if the SIM Clock can be stopped.
This option is depend on your service provider network.
If the clock can be stopped, it could save battery power. Contrary to popular opinion it does not give you free calls!

The service provider lock is used to lock the mobile phone to the SP's SIM card. Once the cell phone is locked to a specific operator, if one inserts a SIM card from a different operator the phone will refuse to accept it! The cell phone will however accept another SIM card from the same operator.
All Nokia phones (2110 and newer) have four different SIM locks which can be used to lock the phone for up to 4 different providers. But most phones with restriction only have one lock activated. The main code used in Nokia phones is:
#pw+(master code)+Y#
This code is able to check, activate or remove Sim card restriction (SP-lock).
Use the * key to get the p, + and w chars.
'Y' has to be 1,2,3 or 4 - depending of what lock you what to deal with.
#pw+1234567890+1# for Provider-Lock status #pw+1234567890+2# for Network-Lock status #pw+1234567890+3# for Provider(???)-Lock status #pw+1234567890+4# for Sim Card-Lock status. (master code) is a 10 digit code, based on the phones IMEI number. You will need to ask your Nokia dealer for your master code number.
To remove restriction on lock 1 type following code:
#pw+(master code)+1#
If you just want to check your phone use 10 random numbers Eg. 1234567890 as the (master code)
To check if phone if restricted on lock 1 type the following code:
#pw+1234567890+1#

To check your phone identity, press *#06#
This will reveal the phone's serial number.

Enhanced Full Rate will give you much better sound quality when you enable it.
The new Enhanced Full Rate CODEC adopted by GSM uses the ACELP (Algebraic Code Excitation Linear Prediction) compression technology. This technology allows for much great voice quality in the same number of bits as the older Full Rate CODEC. The older technology was called LPC-RPE (Linear Prediction Coding with Regular Pulse Excitation). Both operate at 13 kilobits.
*3370# and EFR will be activated after a reboot of the phone ( consumes more power )
#3370# and EFR will be switched off after a reboot of the phone.
Half Rate will give you bad sound quality, which gives the service provider the opportunity to have more calls on the network; and you might get a lower charge from them. (Will give you 30% longer talk-time)
*4720# Half Rate coded will be activated after a reboot of the phone (better standby time)
#4720# Half Rate coded will be de-activated after a reboot of the phone
This does not appear to work on newer models of Nokia phones.