An input assembly (1) for a human interface device such as a keyboard comprises a first membrane (20) having an electrical circuit provided on a surface thereof, and a second membrane (22) having electrical circuit provided on a surface thereof. The first (20) and second (22) membranes are arranged such that the electrical circuits of each membrane are facing each other. The assembly further includes a spacer member (24) provided between the first (20) and second (22) membranes configured to permit selective electrical connection between the electrical circuits of the first (20) and second (22) membranes. An electrical circuit board (50) is connected to the electrical circuits of the first (20) and second (22) membranes inwardly of the peripheral edges of both the first (20) and second (22) membranes, and a housing (70) is provided for enclosing and sealing the electrical circuit board (50). The housing (70) comprises an opening configured to receive the electrical circuit board. The edge of the opening defines an opening perimeter which is sealed to the outer surface of the first membrane (20) to seal and enclose the electrical circuit board (50).