Antenna: Used to receive cellular signal.
Battery Indicator: Shows the battery's charge level. Green indicates a high charge, orange indicates a medium charge, red indicates low charge, and unlit when the battery is empty.
Power Indicator: Green when the device is on, unlit when the device is powered off.
Signal Strength Indicator: Shows the strength of the signal being received. No bars lit indicates no service. Blinking red bars indicates a problem with the SIM card. Solid red bars indicates that the software is updating.
Voicemail Indicator: Used to indicate that a voicemail has been received. Will blink green if a voicemail is waiting.