. The science-history of the universe . legraph. The sending station is at A and one of the receivingstations at B. The line is fed with an alternating currentproduced by reversing commutator, 4. This alternatingcurrent does not affect printing relay 5, but does operatepolar relay 6, which in turn operates the escapement. Re-verser 4 is driven by constant-speed motor 1 and has asmany segments as there are characters on the type escape wheel 10 is provided with an equal number ofteeth, so that each revolution of reverser 4 will produceone revolution of type wheel 7. On the shaft with
. The science-history of the universe . legraph. The sending station is at A and one of the receivingstations at B. The line is fed with an alternating currentproduced by reversing commutator, 4. This alternatingcurrent does not affect printing relay 5, but does operatepolar relay 6, which in turn operates the escapement. Re-verser 4 is driven by constant-speed motor 1 and has asmany segments as there are characters on the type escape wheel 10 is provided with an equal number ofteeth, so that each revolution of reverser 4 will produceone revolution of type wheel 7. On the shaft with thereverser is rigidly mounted a cylinder provided with anumber of pins arranged spirally as shown; each pin is in. 304 ELECTRICITY line with a segment of the reverser and also in line witha pin fastened to the keyboard. Depressing a given key will always stop the cylinderand therefore type wheel 7 in the same place. The con-nection to the motor 1 is made with friction clutch 2,,which slips when cylinder 3 is stopped. Now it is evident. Fig. 45 —Arrangement of a Printing Telegraph or NewsTicker. (From Standard Handbook for Electrical Engi-neers.) if type wheel 7 is started with its characters in certainposition and is rotated by a motor through gear 11 andcontrolled by escapement magnet 6, that it will alwaysremain in the same relative position with cylinder 3, andthat the operator can stop the type wheel in any desiredposition. ELECTRO-MAGNETIC TELEGRAPH 305 If the type wheel stops because of the arrest of thecylinder 3 by depression of a key, the current ceases toalternate and magnet 5 has time to draw up its armature,8, and press the tape against the type wheel, thus printingthe character which corresponds to key depressed at thesending station. These are ingenious arrangements for reproducing ata distant point handwriting, drawings, etc. One of the [Vmwu T I . line HI _ line springs
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