. 
 * Hi Res Display - 320 x 320 resolution 
 * Non-Volatile Memory - Removing the battery causes no memory loss (as long as the device is switched off first, otherwise possible loss of the last thing you edited), on replacing, the device just boots up as if the reset button were clicked.  If a T600 battery ran down completely, you lost the lot. 
 * MP3 Controls - Side buttons adjust MP3 playback volume from any application, third side button pauses playback.  These only work when the keyguard is not active. 
 * Contacts - You can add a photograph to a contact record. 
 * Keyguard - Both the T650 and T600 have better keylock, compared to Tungsten T2. 
 * Silent Mode - Both the T650 and T600 have a ringer on/silence slide switch