:: NOKIA 3210 SECRETS ::  
     
Check the IMEI
*#06# 

Show software version
*#0000# 

Enhanced Full Rate Codec (EFR) activation
*#3370# 

Enhanced Full Rate Codec (EFR) deactivation
*#3370* 

Half Rate Codec activation
*#4720# 

Half Rate Codec deactivation
*#4720* 

Enhanced Full Rate
EFR 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
EFR Half 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.
Sim clock stop.  Only works for 3 minutes.
*#746025625# 

Secret menu
*#92702689#
1) Shows the serial number.
2) Shows when the phone was made mm/yy
3) Shows when the the phone was purchased mm/yy
4) Shows how many times the phone has been repaired.
5) Makes you capable of transferring user data if you have the gear for it
6) Shows how many hours the phone has been on