It's a PC Card connector & supports one Type I or Type II card so you can use PCMCIA cards or CardBus cards
The cards supported are 3.3 V and 5 V PC Card with 68 pin connectors
The D800 uses a TI 7510 CardBus controller
Dell manual: http://support.dell.com/support/edocs/systems/latd800/en/index.htm