A menu control device includes a casing and a roller module. The roller module is installed in the casing. The roller module includes a base, an elastic supporting arm, a scroll wheel, an encoder, a switch element and a microprocessor. The elastic supporting arm is connected with the base. The scroll wheel is pivotally coupled to the elastic supporting arm. The encoder is located beside the scroll wheel. The encoder generates an encoding signal in response to the rotation of the scroll wheel. When an external pressing force is applied to the scroll wheel, the elastic supporting arm is swung toward the switch element, and the switch element is triggered to generate a switching signal. The microprocessor performs an item browsing operation on a menu according to the encoding signal. The microprocessor performs an item selecting operation on the menu according to the switching signal.

A three-stage control mechanism of an explosion-proof switch has a rotating unit and an interconnecting unit. The rotating unit has a first drive portion and a second drive portion that are selectively operated and reciprocated. The interconnecting unit includes a retaining seat and a connecting member. A switch unit is connected to the connecting member. An intermediate sleeve is insertedly connected to the connecting member and extends into the retaining seat. An outer sleeve is tightly sleeved on an outer wall of the intermediate sleeve. The outer sleeve is in tight fit with the retaining seat. A movable cover is provided between the outer sleeve and the rotating unit. A connecting rod assembly includes a first connecting rod and a second connecting rod that are inserted in the intermediate sleeve. The first and second connecting rods are respectively driven by the first and second drive portions.

The invention relates to a user input unit comprising a housing configured to be attached to a base of a user input device, such as a keyboard. The input unit also has a first movable element coupled to the housing, the first movable element being movable along a first direction and user operable second movable element coupled to the housing, the second movable element being movable along a second direction, the second direction being different from the first direction. Further a transmission configured to transfer movement of the second movable element along the second direction into movement of the first movable element along the first direction is provided. The invention also relates to a user input device, such as a keyboard, comprising a base, such a user input unit, and a sensor configured to sense a movement or a position of the first movable element along the first direction.