Key-input mechanisms are disclosed. According to the invention, the support means of the display assembly includes an intermediate support secured to the fixed part of the timepiece movement and provided with support members allowing said at least one display device to be assembled in several positions on the intermediate support. The emitter is configured to generate an electron beam. A tee head on the other end of the axle is fit into a recess in the outside face of the other but to establish a non-rotative connection. The barrier drive ring is rotatable in opposite directions so as to drive the lens barrier member through the neutralizing spring between the open position and the closed position.