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150,840. Thomas, G. H., and Wilkinson, G. S. June 18, 1919. Interlocking and guarding against wrong movements. - Change-speed and reversing gearing drives two independent shafts 26, Fig. 1, and 31, Fig. 2, alternatively, and there is an interlocked control so that the change of driven shafts cannot be effected unless a change-speed lever is in the neutral position. The shaft 26 may drive the road wheels of a motorvehicle, the shaft 31 being mounted in a so-called pillar for starting the engines of aeroplanes, for which purpose the vehicle is stopped with the pillar opposite the propeller of the aeroplane. A countershaft 29 carries a pair of sliding gears 37, 38 adapted to mesh alternatively with gears 35, 36 on a driving-shaft 25. Additional speeds may be provided for. Reversed driving is effected by an idler 40 slidable into mesh with the gears 37, 35 when the double gear 37, 38 is in its neutral position. A gear 46 also slidable on feathers on the shaft 29 may be slid into mesh with a gear 45 for driving the vehicle, or with a gear 44, which is connected through gearing 42, 43 to the shaft 31, for starting the aeroplane engine. The gears 46, 40, and the double gear 37, 38 are operated through forks from selector bars 34, 32, 33. The bars 32, 33 are operated by an arm 62. Fig. 6, connected through a slidable and turnable spindle 58 to the change speed lever 49, which works in a gate 53. The bar 34 is operated by an arm 61 connected through a sleeve 57 to a separate lever 55. A brake 63 is also shown. The lever 55 has a short arm 67, Fig. 9, with two notches 68, 69 by which the lever 55 is locked in its extreme positions by a pivoted spring detent lever 70. When the change-speed lever is brought to its neutral position, a cam 72, Fig. 10, upon an arm 66 upon the spindle 58 engages and depresses the lever 70, so that it is not possible to move the lever 55 unless the change speed gear is disconnected. Specifications 130,019, 131,962, 136,244, and 136,269, [all in Class 7 (v), Internal-combustion engines, Starting &c.], are referred to.