Setting The Output

On an Apple II, the command:
IN#2
tells the apple to get input from card slot 2 as well as the keyboard. This is used to let a serial port "type" a program.

Now, my question is: what is the command to set the output? I've seen it done before, but I can't for the life of me, remember how. This could be used to set the output data to a printer card, or a SSC.

Thanks,
Mark Baldridge