There is a yellow(?) LED on the power unit indicating battery fault. It can be reset with a switch. And you should find a notation on the battery status in the USTACK.
I think the 943B has got some integrated memory, but I don't remember how much.
Does the CPU have a memory brick inserted; an orange (E)EPROM or RAM?
In case your battery is out:
If it's an EPROM there, the program and settings will load from it by power up (if i remember correctly). If it's a RAM or no module, the program will vanish after half a minute by power off.
Kalle