I recently purchased a box of computer hardware from an auction. Among the items is a box that says "Data Switch" and has a knob you can turn to select "A" or "B". I have no idea what this is for or if I have any use for it. Could someone please explain the function of this item? Thanks!

A data switch is a device that will let you connect, in your case, two devices to the parallel or serial port on your computer

It is quite handy, if you have two parallel port printers, say for instance, one ink jet and a laserjet. You could then decide which printer you wanted to print to.

You attach a parallel cable to the input port, and two separate parallel cables from the switch to each of the printers.

You then use the switch the knob to determine which printer is printed to

btw, It doesn't just have to be printers, it could be any parallel device

you could have an older IOMEGA zip drive and a printer, etc etc