'648 



means, it is bellei- lo try to irnproxe the traiisinilter. As a matter of 

 fact present let'liiiifiue is actually capable of pioduciiig transmitters 

 whicli keep their wave practically constant. 



The advantages of the reception by galvanometer in distinction 

 from the reception by telephone are worth mentioning. On trans- 

 mitting slowly it will be possible to receive signals with the gahano- 

 meter, which are not readable by telephone. Every improvement in 

 this direction of the receiving a|)|)aratiis, which always remains 

 relatively simple, saves, as Austin') observes rightly, large sums 

 needed both for the erection ot high power sending stations and for 

 their working expeii.ses. And that, as matters stand at present, im- 

 provements are still wanted, is obvious from tiie many ditïiculties 

 experienced even with the best installations. To qnote an example it 

 may be noticed, that during the whole of July J 921 the communi- 

 cation between two of the Trans-Atlantic stations, whicli are con- 

 sidered among the most reliable, was so poor thai only 23 per cent 

 of the words sent were successfully received'). 



The high speed reception with the galvanometer makes it possible 

 to take full advantage of the installation at those hours of the day 

 and the night, which are the most favourable for the transmitting 

 of the signals, and to transmit many more words than could be 

 received by telephone. Moreover the secrecy of the telegrams can 

 be belter secured since the numerous telephone-receivers will not 

 be able lo read the quick signals. 



In time of war the intei'ference by a second .station will be hin- 

 dered, when the signalling wave and Ihe non signalling wave of 

 an arc lransn)itler are received simultaneously with two galvano- 

 meters. 



Finally we may mention another advantage which bears upon 

 the general use of wireless telegraphy in Ihe world. It is Dr. de 

 Ctroot, who has placed it on the fore-gronnd. During night and day 

 numerous signals are sent from many hundi'etls of transmitters. The 

 installations interfere with one anothei', if they use waves the lengths 

 of which do not greatly differ. The diiference in wave-lengths which 

 are applicable for transmitting signals is limited; only these waves 

 are useful, which range neither below nor above a certain length; 

 in other words; I he spectrum of the useful waves is comparatively 

 small. Everyone using a part of it takes it away from another man. 



1) Gonf. L. W. Austin, Long distance radio communication. Journal of the 

 bVanklin Institute, Vol. 193, Apr. 1922, p. 437 (458). 

 «) Gonf, L. W. Austin I.e. p. 443. 



