Commodore CD1401 & CD1405 Propriatry Memory Cards.

These cards are called "Proprietary Memory Cards" or sometimes "Personal Memory Cards" which is a term you may not be use to, This card acts like a memory card on a modern games console, In its normal state it is used to save game scores but can be mounted as a separate drive (Like an electronic floppy) or Added to the CDTV's main memory. If you mount it as a drive then you can install a boot code onto the card so when you reset you can boot off it into a CLI mode or (If you have the 256 Kb version) load Workbench or even install small games .
The card comes in two versions, A 64 Kb card (The CD1401) and a 256 Kb version (The CD1405), 256 Kb is the limit as the address space for the memory card has to be available even if you do not have a card fitted so although the space for up to an 8 Meg card could have been allocated it would have meant that no other card could be fitted (For example the Bigram CD8 could not have existed).
The card was available from most CDTV outlets when new but was very expensive even for the 64Kb version so they are very rare to find second hand.

The card plugs into the CDTV just under the LCD display, a black plastic cover hides the slot when not in use. (It can be put back on after the card is fitted as well) The card is automatically sized up and pointed to the assigned space where it will wait until it is used, The driver is embedded in the CDTV`s Prom so you don't need to install anything to get the card to work but if you did want the card added as system memory software would be needed, Commodore also made software to make the cards bootable, All hand written in Assembler to make it extra small so even a 64 Kb card will boot the CDTV.

The card comes with a little green screwdriver and battery, The battery keeps the memory chips powered while the CDTV is turned off or the memory card is removed, The screwdriver is to unscrew the tiny screw that holds the battery tray in place.
The card also has a little switch, This switch is a write enable/disable, If you mount the card as system memory or are copying data to the card it must be write enabled otherwise it is best to write disable it else the card can be wiped for example if you mount it as memory after playing a game of SimCityİ

One note is that the slot this card goes into is not a PCMCIA slot (As found on the A1200, A600, CDTV CR and most laptops) so don't go plugging a PCMCIA card in there as the power line could line up very well with a nice data line and fry your expensive card, The same goes for trying to copy data from a CDTV to a laptop with this card, If you put a CD1401 or CD1405 in a laptop don't expect either to survive, Both have a power supply (Unlike a PCMCIA card) so the CDTV card will cook your laptop while your laptop will cook your CDTV card, Nice. :)