Abstract: A process for fitting at least one metal piece, which has at least one cylindrical bore, around a metal tube, in particular a metal cam shaft, as used, for example, in an internal combustion engine. The process includes clamping the metal piece in the assembly unit and introducing the metal tube into the bore of the metal tube with one end of the tube bearing upon the retractable stop. After expansion of the tube to fix the one metal piece on the tube, and the retractable stop is retracted before any additional metal pieces are fitted to the tube.

Abstract: A transmitter for multiplexing three optical channels at different wavelengths has (a) first, second and third laser diode means delivering linearly polarized optical beams at respective wavelengths .lambda.2, .lambda.3 and .lambda.4 which are mutually different; (b) an assembly located in the path of the light of wavelength .lambda.2 emitted by said first diode means and including a plate which is substantially quarter-wave for the wavelength (2 .lambda.2-.lambda.4), a filter having a band pass centered on wavelength .lambda.2, a plate quarter-wave which is substantially for wavelength .lambda.4 and a polarizer, the first diode means being oriented so that its beam is transmitted by the polarizer. A first light beam combiner directs light from said third diode means onto the polarizer along a direction of 90.degree. from the direction of the beam of wavelength .lambda.2 and with the same polarization direction, so that the beam of wavelength .lambda.4 is reflected towards said filter.

Abstract: A transmission with free-wheel capability comprises a bolt slidingly mounted in a bell-housing integral with a driving shaft, adapted for engagement in a cage provided with rollers and mounted in the bell-housing for movement between two positions in which the rollers and the bell-housing are in abutment so that a driving and a driven shaft are coupled to rotate together. The bolt maintains the cage in a middle position in which the driven shaft is disengaged and allowed to free-wheel, when the transmission is in forward travel and not in any braking condition. An electromagnet draws the bolt into the cage. This device ensures the free-wheel setting of the vehicle in forward travel up to a predetermined speed. At higher speeds a safety system automatically couples the driving and driven shafts together again.