1914] on Improvements in Long-Distance Telephony ill 



and the other is connected to the diaphragm of a telephone. The 

 liquid falls on to one plate and bounces off on to the other, and 

 makes an electrical connection between them. The movement of 

 the diaphragm sets up oscillations in the liquid column and also varies 

 the distance between the plates, and therefore alters the thickness of 

 the connecting film of liquid, and hence its electrical resistance. If 

 one of these plates is connected to a transmitting antenna and the 

 other to the earth we have the means of varying the resistance in 

 the antenna circuit, and hence the amplitude of the emitted electric 

 waves so as to modulate them in accordance with the wave form of 

 the speaking voice. 



At the receiving end the arrangements are not different from 

 those used in wireless telegraphy employing telephonic reception. 

 The receiving antenna is coupled to a condenser circuit, which has 

 in it a crystal or Fleming valve receiver and a telephone. 



The valve rectifies the continuous waves, but the uniform current 

 produced does not j;er se affect the telephone. If, however, modula- 

 tions of amplitude are produced in the radiated waves by speaking 

 to the transmitter at the sending station, the receiving telephone 

 is affected by these variations of amphtude, and responds only to 

 the waves on the waves or variations in the amphtude of the 

 continuous waves. The receiving operator then hears the words 

 uttered to the distant transmitter. 



The limiting factor is therefore the current-carrying power of the 

 speaking microphone or transmitter. 



Using his liquid transmitter, Professor Yanni has achieved the 

 feat of speaking successfully from Rome to the Island of Ponza 

 (120 km.), to Maddalena (260 km.), to Palermo (420 km.), to Yit- 

 toria (600 km.), and finally to Tripoh (lOUO km.). 



The timbre or quality of the voice is said to be reproduced with 

 great accuracy. Since all electric waves travel at the same speed 

 through space and attenuate proportionately, there is little or none 

 of that distortion to which we have referred in the case of telephony 

 along wires. 



Time will not permit of reference to the details of all the experi- 

 ments on this subject made by Fessenden and others in the United 

 States, Poulsen in Denmark, Ruhmer, Goldschmidt, and the Tele- 

 funken Company in Germany, M.M. CoHn and Jeance in France, and 

 Marconi, Majorana and Yanni in Italy, and Ditcham in England. 

 Suffice it to say that this lineless telephony has been successfully 

 conducted up to 500 or 600 miles distance. 



The chief difficulty in obtaining greater ranges is that of con- 

 structing a voice-varied resistance or so-called microphone transmitter 

 which shall be able to carry large currents up to 50 or 100 amperes 

 and vary these currents faithfully in accordance with the wave form 

 of the speaking voice. 



Wireless telephony across the Atlantic will be achieved when 



