A single device operable as a controller with multiple functions includes a mounting member, a control member, a first switch, a second switch, a third switch, and a processing unit. The control member can be pressed and rotated with respect to the mounting member. The first switch, the second switch, and the third switch are located on the mounting member. The processing unit is electrically connected to all the switches. The processing unit receives a first control signal from the first switch when the control member is pressed, a second control signal from the second switch when the control member is rotated clockwise, and a third control signal from the third switch when the control member is rotated counterclockwise.