4/2 



NATURE 



[December 9, 1920 



Automatic Printing of Wireless Messages. 



ONR of the recent developments in wireless 

 ifk'graphy, which, as we have already an- 

 nounced briefly, was demonstrated by Mr. 

 A. A. Campbell Swinton duringf his address on 

 Xovember 17 to the Royal Society of Arts, is the 

 automatic printing of wireless messages in roman 

 type. Several systems of printing telegraphy are 

 in use on ordinary lines, but the ingenious method 

 designed by Mr. F. G. Creed is, we believe, the 

 only one that has been adapted to the printing of 

 wireless messages. High-speed wireless reception 

 in various forms is being used to an increasing 

 extent, and Morse code messages are recorded by 

 optical and mechanical methods, as well as by 

 :in instrument analogous to a phonograph; but 

 the actual printing of the words in ordinary type 

 on a paper strip presents obvious and very great 

 advantages. 



That this result has been rendered possible of 

 achievement is mainly due to the greatly improved 

 methods of amplification of the signals received 

 now available, which have enabled current im- 

 pulses of sufficient strength for the actuation of 

 the necessary relays to be obtained from the 

 minute oscillations in the receiving aerial. Briefly, 

 the system consists in a combination of the exist- 

 ing printing telegraph apparatus designed by Mr. 

 Creed with the latest arrangements of groups of 

 thermionic valves such as those devised by 

 Capt. L. B. Turner and other workers, who 

 carried on important researches in this direction 

 during the war. 



In the Creed system, whether for wireless or 

 line transmission, the message is first translated 

 into the Morse code by punching a perforated 

 strip of paper in an apparatus, with a typewriter 

 keyboard, so contrived that each key perforates the 

 strip, by a solenoid operated mechanism, with the 

 Morse equivalent of the letter in question. This 

 strip, exactly as in the case of automatic Wheat- 

 stone working, is passed through the transmitting 

 instrument, which sends out current impulses in 

 the ordinary way in the dots and dashes of the 

 Morse code. These, in ordinary telegraphy, go 

 direct into the line, but in wireless working they 

 are used to actuate a special transmitting contact 

 maker, forming the equivalent of a high-speed 

 relay-operated Morse key. Messrs. Creed and Co. 

 have developed several sizes of transmitters for 

 this purpose, including one suitable for very 

 powerful installations, worked by an electro-pneu- 

 matic relay arrangement, and capable of dealing 

 with as much as 300 kw. This has eight sets of 

 contacts in parallel, each breaking under a power- 

 ful air-blast. 



The waves at the receiving station are picked 

 up by a thermionic-valve receiver, and consider- 

 ably amplified by a number of valves in cascade in 

 the manner employed in connection with other 

 methods of recording. Current impulses are thus 

 supplied to the relay magnet, forming part of the 

 apparatus known as the Creed receiving perfor- 

 NO. 2667, VOL. 106] 



ator. This is of the same form as that used in line 

 ! telegraphy, and, as employed hitherto for wireless 

 reception, is worked by compressed air, although 

 the company is now developing an electrically 

 driven pattern on a mechanical principle, which is 

 simpler and more compact, and dispenses entirely 

 with compressed air. The Creed air-engine relay 

 used in the instrument is a very interesting piece 

 of apparatus. The tongue of the electrical part 

 of the relay, instead of operating electrical con- 

 tacts, actuates a very small slide valve controlling 

 a little auxiliary piston, which moves the slide 

 valve of the larger main piston. This, by moving 

 in one direction or the other, drives forward one 

 or other of the perforating punches, through a 

 system of levers. 



A very ingenious device arrests the motion of 

 the strip while the holes are being punched. The 

 strip from the receiving perforator, which is still 

 in the Morse code, is the exact counterpart of that 

 used at the transmitting station, with holes side 

 by side to indicate dots and staggered to repre- 

 sent dashes, and a continuous row of holes down 

 the centre for feeding purposes. The arresting 

 action is effected by a plunger being thrust for- 

 ward between the teeth of a spur-wheel on the 

 sliafi of the feed-sprocket. The holes are punched 

 opposite each other if the second punch moves 

 forward soon enough after the first for this wheel 

 not to have advanced a whole tooth pitch, so that 

 the arresting plunger, in reaching the bottom of 

 the space between the teeth, really brings the 

 paper back a little way. On the other hand, if 

 the wheel has advanced by a whole tooth pitch 

 or more, the plunger engages in the next space, 

 and the second perforation Is advanced beyond 

 the first. A Creed receiving perforator is seen in 

 the centre of Fig. i. 



The perforated strip is then passed on to the 

 Creed printer. The great featiye of this remark- 

 able piece of apparatus is that it forms an auto- 

 matic typewriter controlled entirely by the position 

 of the holes in the perforated strip, and translates 

 Morse code into printed characters. It is impos- 

 sible here to do more than to indicate the general 

 principle on which the instrument works, 

 although it is on the perfection of the design of 

 details that much of its success depends. In 

 Fig. I the strip from the perforator is seen passing 

 direct to the printer, and a printer by itself is 

 shown in Fig. 2. 



The perforated paper strip is fed past a group 

 of spring selecting needles, ten on each side, and 

 when it is momentarily at rest with the portion 

 corresponding to a letter opposite the needles, a 

 certain number, forming a pattern corresponding 

 to the letter, protrude through the holes in the 

 strip. Each needle which has thus advanced 

 causes, in a way indicated later, a change in the 

 position of one of a pack of thin steel strips or 

 sliding valve plates. These valve plates lie 

 between two fixed perforated plates, and are 



