Modem Operation Mode.
The following enumerated values are supported:
online(0) - Device can acquire a system and make calls.
lowPower(1) - Device has temporarily disabled RF.
factoryTest(2) - Special mode for manufacturer tests.
offLine(3) - Device has deactivated RF and is partially shutdown.
reset(4) - Device is in the process of power cycling.
shuttingDown(5) - Device is in the process of shutting down.
persistentLowPower(6) - Device has disabled RF and state persists even after a reset.
modeOnlyLowPower(7) - Mode-only Low Power.
unknown(255) - Unknown.