Abstract: A vibration tamper device in which a frame having spaced wheels on a horizontal shaft on which a rocker is tiltable in a fore and aft plane and has tamper feet at the opposite ends. An engine supported on the shaft drives a reciprocatory member which is connected to the rocker to oscillate the rocker and cause the tamper feet to engage the ground alternately. A one way clutch is preferably interposed between the rocker and at least one wheel so the device will move as the rocker oscillates.

Abstract: A thyristor circuit for converting direct current to alternating current in which thyristors connecting opposite sides of a direct current circuit are alternately ignited while a commutating branch connected in parallel with the thyristors has further thyristors which are ignited alternately to extinguish each of the first mentioned thyristors before the other is ignited. The commutation branch includes two serially connected inductors interposed between the further thyristors which are bypassed by a damping diode. The juncture of the inductors is connected by a capacitor with the alternating current output line. The commutating branch may be supplied by a separator direct current voltage source which is coupled to the first mentioned direct current source by way of a diode.