GB311711A - Improvements relating to copying telegraph systems - Google Patents

Abstract

311,711. Kolster-Brandes, Ltd., (Assignees of Broker, W. M.). May 14, 1928, [Convention date]. Copying-telegraphs.-In a copying-telegraph apparatus a plane surface is scanned with light from a. stationary source, the light being focussed on the surface by a lens oscillating in an arcuate path, the light passing through the surface and then being directed on a stationary photo - electric element. At the transmitter, Fig. 1, light from a source 16 travels along a hollow tube 21, rotatable in bearing 22 and carrying hollow extensions 18, 19 perpendicular to the axis. The light is reflected by prism or mirror 24 along the tube 19, is focussed by lens 27 on to the translucent document 13 supported on a glass sheet 38, is then collected by lens 28, reflected by mirror 29 along tube 18, and finally reflected at 31 on to a photo-electric cell 11. A cam 33 driven by a motor 34 drives an arm 36, which oscillates the arms 18, 19 at a definite rate to and fro across the document 13. The document 13 is advanced a small distance perpendicular to the scanning motion either continuously or intermittently at the completion of each swing of the scanning arms. The light from source 16 is modulated at an audible frequency, say 1000 cycles, by a perforated tone wheel 39 driven by motor 41, and interposed at some point between the light-source and the photo-electric cell. An amplifier 43 has its input connected to the cell 11, and its output to a radio-frequency modulator 44 associated with a master oscillator 46, the modulated output being passed through amplifier 47 and impressed on a transmitting aerial 48 At the receiver, Fig. 2, the incoming signals are amplified and impressed on a spark gap apparatus 56, comprising two electrodes 58, Fig. 4, supported by an insulator 57 formed with an annular ridge 59, which rests on the photographic paper 54. The unit 56 is mounted on an arm 67, oscillated by cam 69 and rod 72 in synchronism with the transmitting mechanism. The paper 54 is also advanced in synchronism with the document 13 at the transmitter. Synchronous movements.-A synchronizing frequency is radiated by the transmitter, once for every complete cycle of the scanning mechanism at the transmitter, as follows. The arm 18 at the end of its swing closes the switch 74, which impresses a modulating frequency differing from the tone frequency of the wheel 39 upon the modulator 44. At the receiving station the cam 69 is driven through an overrunning clutch 78 at a slightly greater speed than the transmitter cam 33, and the synchronizing signal is selected from the amplifier 53 by a filter 76, and actuates a tripping solenoid 77 which allows a member 79, carried by the cam 69, and normally engaged by the solenoid rod, to rotate for another complete turn.