| 摘要 |
287,844. Telefunken Ges. f³r Drahtlose Telegraphie. March 26, 1927, [Convention date]. Copying-telegraphs.-In a copying-telegraph or the like comprising one or more light-sensitive devices, such as a photo-electric cell 5, one or more additional compensating light-sensitive devices 9 are arranged so that the effective output is substantially zero during light shades of a picture or the like 4 and increases with increasing darkness of shade in the picture. The invention facilitates the direct reproduction of a positive by an electro-chemical or photographic receiver. The photo-electric cells are connected in a bridge circuit which is balanced for light shades by adjusting the light falling on the compensating cell by moving a mirror 6 which reflects light from the beam falling on the cell 5, or by an iris diaphragm, or by an absorption wedge. The carrier frequency is produced bv a rapidly rotating perforated disc 7, or by a. source of alternating potential in series with a source of direct potential 10 (Fig. 2. not shown).
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