Input device adapted for an electronic device

An input device adapted to an electronic device, the electronic device having a housing, the housing having a major input area and a secondary input area, the input device being installed on the secondary input area and comprising:

• a casing having a first face and a second face opposite to the first face;
• a first input module disposed on the first face;
• a second input module disposed on the second face;
• and
• a fixing mechanism disposed on at least one of the casing and the housing, the fixing mechanism fixing the casing when the casing is installed in the secondary input area with the first face being oriented toward the secondary input area, such that the first input module is contained in the housing and the second input module is exposed from the secondary input area, the fixing mechanism fixing the casing when the casing is installed in the secondary input area with the second face being oriented toward the secondary input area, such that the second input module is contained in the housing and the first input module is exposed from the secondary input area.