Unlike most other ports present on the PC, the Game port is an analog port. This means that signal first needs to be changed to digital form, a task which is usually done by an analog-to-digital converter. In the early days, most joystick designs were digital, which made them easier to build and cheaper. The game port has a 15-pin DSUB interface, most home computers that used digital joysticks had a 9-pin one. This made existing joysticks incompatible with the new interface.