*#06# : IMEI number (International Mobile Equipment Identity)
*#2254*# Status register: C, BS, RR, MMI, CREAT.
*#2255*# : Activate and deactivate the "DEBUG CALL"-Mode. When activated, make a call to a busy line and the phone will display some hex-codes on the display.

*#2558*# : Time in days,hours and minutes you are connected to the net.
*#2562*# : Not clear. The phone reconnects to the net.
*#2565*# : Not clear. Warmstart ?

*#3333*# : (NO) BLOCKING - list (15 items)
*#2377*# : "BEER": Not Clear, the phone waits a random time and reconnects to the net, sometimes the phone makes a reset or something
*#3377*# : Init, Flags, SIM LCK

*#3353*# : Resets the (NO) BLOCKING - list
*#7378*# : Name, Length, SIM phase
*#7489*# : SECURITY CODE

*#7693*# : You can activate and deactivate the SLEEP MODE (when deactivated the battery will go down.)
*#7787*# : Not clear: SPURIOUS INTERRUPT
*#7948*# : SWITCH OFF: Not clear. It is a timer or something
*#8463*# : Some information about the SLEEP MODE: Wake, Sleep Req., Sleep

Philips Genie (TCD838)

Type *#2337*# and it will be activate the beep signal when the cellphone reconnected to the net.