Abstract: There is disclosed a high-voltage DC circuit breaker apparatus with reverse current insertion system by line voltage charge, which comprises a commutation switch, a series circuit of a capacitor, a reactor and a switch connected in parallel with the commutation switch, a resistor connected so as to charge the capacitor by a line voltage. The charging time constant of the capacitor determined by the capacity of the capacitor and the resistor is used as a reference in a manner so that the rise time constant of the line voltage is smaller than the charging time constant of the capacitor, and the rise time constant of the line current is larger than the charging time constant of the capacitor, thereby interrupting the fault current without fail.

Abstract: A number of elementary units each including an elementary plate member are arrayed in rows and columns to provide a screen, with each elementary plate member pivotally supported so as to be independently reversible as to its front and rear faces to be exhibited to the viewer. Both faces of each elementary plate member are imbued with different colors clearly distinguishable from each other. Pneumatic actuating means comprising air nozzles or slide valves for producing controlled currents of air under pressure are arranged behind the array of elementary plate members in a manner such that the elementary plate members are selectively reversed as to their front and rear faces, in the order of successive rows or columns, for the display of any desired graphic or alphanumeric pattern. The elementary unit itself can be used as a display device if the front and rear faces of the elementary plate bear necessary letters or patterns thereon.