A field emission device includes a cathode, an anode, an emitter, a first adjusting electrode, and a second adjusting electrode. The pulley has a belt-driving section configured for engagement by the belt and a belt-guiding section integral with the belt-driving section. A timer can be preset to a selected time at which the control shaft is to be turned from an off position to an on position. A physical location may include an edge or a central region of the memory array or the memory die.