881,891. Photoelectric synchronization of camera shutters. ASKANIA-WERKE A.G. Oct. 8, 1959 [Oct. 9, 1958; Oct. 10, 1958], No. 34165/59. Class 40(3). [Also in Group XX] In a system for controlling the synchronous operation of camera shutters of the venetian blind type located at a plurality of specially separated cinetheodolite photogrammetric posts, so as to make simultaneous exposures at all of said posts, means are provided for generating a series of single electric camera release impulses and for transmitting such impulses to all of said posts by wire or wireless, the shutter of each said post is coupled with an electric impulse generator and transmitter which in a predetermined position of the shutter serves to transmit a feedback impulse or signal to an observation apparatus and adjustable impulse delay means are provided in the transmission for said camera release impulses to each post. In one arrangement, the shutter release impulses are transmitted from a central control post and each cine theodolite post is equipped with a manually adjustable delay means and an observation apparatus comprising a cathode ray oscillograph on which the feed back impulses are displayed. The delay means are then adjusted to obtain registry between said feedback impulses and datum impulses which are also displayed on said cathode ray oscillograph and which are transmitted to each cine theodolite post for releasing flash lights serving for photographically recording at each theodolite information from scales relating to the elevation and bearing angle of the respective theodolites. In a second arrangement, all the delay means are accommodated in the central control post, the shutter release impulses after their various delays are separately transmitted to the respective theodolite posts, and a single cathode ray oscillograph is provided at the central control post. In this case all the feedback impulses are transmitted back to the central control post for display on the single cathode ray oscillograph and may be registered one with the other instead of with datum marks. In a third arrangement, the delay means are located at the respective theodolite posts and are remotely controlled from the central control post by means of sound of particular frequencies and of more than a certain minimum duration, a single cathode ray oscilligraph being provided at the central control post. In all these arrangements impulse recording apparatus may be provided in addition to the cathode ray oscillographs. The venetian blind shutter (Fig. 2) comprises rotatable slats (for example 3, 4, 5) having pinions 6, 6<SP>1</SP> engaging with racks 7, 7<SP>1</SP> on a frame 2, said frame being slidable between stops 25, 26, being tensioned alternately by springs 14, 15, and being held in the alternate tensioned positions by successive engagements of a stop 8 on the frame 2 with a stop 9 on an armature 10 which is pivoted for shutter release about an axis 11 against the tension of a spring 13 when an electromagnet 12 is energised by a shutter release impulse. The slat 4 has on its axis an electrical contact maker 29 for the production of feedback impulses when said slat is in its vertical, i.e. open position. Alternatively, a photoelectric cell may be placed behind the slats for this purpose. The springs 14 and 15 are alternately tensioned by means of a lever 17 which is pivoted about a shaft 20 and is coupled by way of a manually disengageable clutch arrangement 22-24 with a further lever 19 which is also pivoted about a shaft 20 and which is continuously oscillated by means of an eccentric 18 on a rotating shaft 16.