Info Sim Clock Stop :-

To view if sim clock can be stoped enter *#746025625# [*#sim0clock#] (Sim-clock-stop is a kind of standby mode which will save battery time) May not work with all firmware versions.
              
                 Enhanced Full Rate/Half Rate Enhanced Full Rate Codec :-
                (EFR) For activation enter *#3370#
                 For deactivation enter *#3370*
                 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 ASELP (AlgebraicCode 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.(but you take up more space on the network, so they can charge you more) - Talk-time is reduced with about 5%

                 Half Rate Codec
                 For activation enter *#4720#
                 For deactivation enter *#4720* In all cases the phone will automatically restart.
                 Half Rate will give you bad soundquality, which gives the serviceprovider 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.

                 Imei Code :-
                 To View IMEI (International Mobile Equipment Identity) enter *#06# Firmware Versions   
                 Check To view the Firmware version enter *#170602112302#
   
                 Restore Factory Settings :-
                 To restore factory settings (Memory, language, counters not included) enter *#7780#
                 Manufacturer Information To view Week and Year of manufactureenter *#3283# [*# D A T E #] The last two digits are the year. If the year is 95, the first two digits are the month. For 96 the first two digits are the week of the year.
                 Firmware Version :-
                 To view the firmware version enter *#170602112302# or *#9999# On newer phones, the code has been changed to *#682371158412125#