A number of special controllers designed for use with specific games were released for the system, though very few such devices proved particularly popular. Such devices included, but were not limited to, the Zapper (a light gun), the R.O.B., and the Power Pad. The original Famicom featured a deepened DA-15 expansion port on the front of the unit, which was used to connect most auxiliary devices. On the NES, these special controllers were generally connected to one of the two control ports on the front of the console.
How were the special controllers connected to the NES?
control ports on the front