Clyde93 :
My fault I mean to say output. Can the second card because used as a output.
No the second card cannot be used as an output if you are using the same model gpus and SLI. Nvidia control panel automatically detects your SLI and force everything to go through your first primary card on the top PCI-e slot. But you can always buy another DVI cable and attach that to your primary card and set it up as a dual monitor.
There is only of one instance that I know where you can use your second card as a secondary monitor is when you use 2 different GPU's not in sli or crossfire config. By default gfx software will use the top pcie slot as primary and disable any other gpus in other slots. But to work around that you have to configure windows display properties and google for a software that works around that issue.
But for SLI or crossfire, only the primary card is the default display.