Dual Systems -- CMEM RAM Board
This Dual Systems board contained a battery backup capability to store RAM data after the system was powered down.

You could store up to 32K of memory on the board and the data with battery backup could last for up to 3-10 years! The board was IEEE-696 compatible and ran fast (220 nanosecond RAMs). At speeds up to 6MHz for both 8 and 16 bit systems.  There was extended memory addressing through 24 bit address lines.  The board also had bank select capability and unusually via software you could write protect window segments of RAM.  The board was switch selectable addressing to any 4K boundary and could generate interrupts when a power failure was detected. This was a very nice board even though it was only 32K.

I cannot locate a manual for this interesting board. If you have one please let me know.