Patent GB-306961-A (GB)
Title: Apparatus for effecting the distant transmission and the reproduction of images
IPC: H04N3/04
Filed: 1929-02-27
Abstract: 306,961. Thuau, U. J., and Antranikian, H. Feb. 29, 1928, [Convention date]. Copying-telegraphs.-In a picture-telegraphy apparatus using a band travelling forward without helical motion for supporting the picture to be transmitted, and a sensitized similar band for reception, a pair of synchronously rotating discs carrying lenses are used to scan paths on the transmitting and receiving bands respectively. In the transmitter, Fig. 1, the band 23, carrying the pictures, passes over rollers 3 driven by motor 21, through gearing not shown, which also drives a disc 1 carrying a row of lenses 2. Light from a point 7 on the hand 23 is focussed on a hole 6 in screen 5 through which it passes to a photoelectric cell 4, which controls the output of a telegraph or wireless transmitter 22. Thus each lens 2 scans a line 8 on the transmitting band, each line being a set distance, controlled by the gearing, from that just scanned by the previous lens. At the receiver, Fig. 2, a light-source 12 controlled in known manner by the incoming signal impulses projects a luminous spot 7<1> on the moving sensitized band 23<1>, through the hole 6<1> in the screen 5' and one of the lenses 2', which are arranged on a rotating disc 1<1> geared to roller 3<1> as in the transmitter. Each lens thus scans a path 8' corresponding to path 8 in the transmitter. The path 8 may be made any shape by converting the holes 6 and 6<1> into a slot 6<11>, Fig. 3, and placing in front of the moving bands 23 and 23' a screen 26 having a slot 27 of the desired shape, or in the case of the transmitter by illuminating the band only along a line of the desired shape. Synchronous movements.-Synchronization of transmitter and receiver is effected by impressing on the cell 4, Fig. 1, at the period when lens 2 is scanning a region at the side of the moving band, an intermittent illumination from a lamp 13, rotating notched disc 17 geared to disc 1, and perforated screen 15 placed in this scanned region. At the receiver, Fig. 2, the impulses due to this intermittent illumination reappear as fluctuations in the light-source 12 and either are completely extinguished by a rotating notched disc 17<1> corresponding to disc 17, Fig. 1, or affect the photoelectric cell 18, the current from which, after rectification and amplification, excites a field winding 20 of a machine 19 coupled to the driving motor 21. The other field winding 28 of the machine 19 is preferably provided with a slightly greater and opposite exciting current, so that depending on the illumination of the cell 18, the machine acts as an accelerating motor or a braking generator, the synchronous mean speed attained being steadied by a flywheel. Alternatively the armature of the machine 19 is shortcircuited through a resistance and acts as a variable brake controlled by the cell 18, the motor 21 being set to run slightly faster than synchronous speed. The machines 19 and 21 may be combined to constitute a single machine. The synchronizing light-beams may be diverted to. the edge of the moving band by lenses, prisms, or mirrors if the synchronizing apparatus is removed from a position near the band.