NI PXI/PCI-5401/5411/5431
LOCK and ACCESS LEDs

The NI 5401/5411/5431 signal generators have two LEDs: LOCK and ACCESS.

LOCK LED

The LOCK LED indicates basic hardware status.

Color	Indications
Off	The device phase-locked loop is currently not locked to a Reference clock source. This status is normal if the device has not been programmed to phase lock to a Reference clock source. This is an indication of a problem if the device has not been programmed to phase lock to a Reference clock source.
Amber	The device phase-locked loop is locked to the selected Reference clock source.

Note  For more information, refer to Phase-Locked Loops and Module Synchronization.

ACCESS LED

The ACCESS LED indicates the device state.

Color	Indications
Green	Indicates that the device is powered.
Yellow	Indicates that the computer is currently accessing the device.