582,705. Electric synchronizers. MIDGLEY, A. H., and GREY, D. J. Oct. 28, 1940, No. 15801. [Class 40 (iii)] [Also in Groups XXI and XXXVIII] The time fuze of a shell is set after the shell has been placed in the gun and at the instant of firing in order to obviate the error which occurs in the time interval between setting the fuze and inserting the shell in the gun and firing. The setting of the fuze and the operation of firing are under the control of a predictor, the indicating arm of which coacts with a synchronizer external to the gun and reproducing the position of the setting mechanism. The means employed comprise a setting clockwork mechanism e for setting the race c which is slotted to receive a " hand " b on a " timing " mechanism a which causes detonation and bursting of the shell. The setting mechanism is slidably mounted in the shell body so that when the shell is fired, the setting mechanism moves backward due to inertia and the race c is locked by pins in the position regulated by the predictor arm. The race c is also provided with a stop h adapted to contact a fixed reed g once in each rotation and the sound is adapted to be transmitted by a microphone i through an amplifying set il to a magnet m. This magnet is adapted to operate a sliding arm l having two stops l<1>, l<2> adapted to contact with notches kl, k2 respectively of a double cam mounted with friction on the spindle of a gramophone motor having a fly-wheel k. The cam carries a contact n of the firing circuit, the other contact being constituted by the adjustable arm p of a predictor. If the speed of the fly-wheel k is faster than that of the race c, the stop l<1> engages the notch on the cam and reduces it, while if the speed of the fly-wheel is lower than that of the race c, the pin l<2> engages the inclined notch k<2> and forces the speed up, so that this gear acts as a synchronizer to the setting gear rotation. The action is as follows : the fly-wheel k is set in rotation and a clutch r<2> in the shell head is released by magnetic action as the shell is inserted in the gun so that the setting gear is released and the race c is rotated. At the first impulse due to the reed, the electromagnet m. is influenced to attract the bar l and the cams revolve with the fly-wheel and the speed is synchronized with that of the race c. As the firing switch o is closed, the gun will fire as soon as the contact n makes with the arm p and the setting gear is locked by pins, the inertia causing it to slide in the shell as the shell leaves the gun. The timing mechanism a is automatically started at this instant so that the detonating arm b now begins to rotate and after an interval it is in alignment with the recess in the setting race and so detonates the shell, the angle between this recess and the arm having been controlled by the synchronizer k and predictor arm p.