Means that your machine is trying to call Batman? Your machine's Parameters, Programs, Offsets, etc. are stored in RAM. This RAM clears out when you power down. However, you have batteries which keeps them saved while you are powered off. If the batteries go dead then when you power off all of your Parameters, Programs, Offsets, etc are deleted. This BAT alarm is warning you that IF you power down (because your batteries are weak) you will lose all of your Parameters, Programs, Offsets, etc. DO NOT POWER OF FOR ANY REASON TILL AFTER THE BATTERIES HAVE BEEN REPLACED. Most older CNC used "3" D Size alkaline batteries. They are in a Black rectangle shape case with FANUC written on the outside. Typically its mounted on the outside of the main cabinet door. Sometimes inside the main cabinet itself. If you can not locate it there is white plug on the main board with two wires in it that goes to the battery box. Just follow where it goes. The alarm may not reset till after you cycle power once the new batteries have been installed. MAKE sure that they are installed correctly or all memory will be lost. Make a backup of everything now before you turn it off in case you have a bigger problem than just dead batteries.