1920] Thermionic Valve in Wireless Telegraphy & Telephony 183 



deflects away the electrons proceeding from the filament and prevents 

 them reaching the collecting plate. If, then, we connect the poten- 

 tial plates to the ends of a resistance of about 15,000 or 20,000 

 ohms, and include this resistance in the plate circuit of an ordinary 

 three-electrode valve, the thermionic current of the latter flowing 

 through the resistance will create a terminal potential difference 

 which arrests the thermionic current of my new valve. Hence the 

 relay does not operate. If, however, we give an extremely small 

 negative potential to the grid of the three-electrode valve, then this 

 reduces the thermionic current of the latter and increases that of 

 the other valve, which again in turn causes the relay to close contact, 

 and it may be thereby caused to ring a bell. The negative grid 



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Fig. 18. — Arrangements for a Wireless Electric Bell Call 

 employing a four-anode valve. 



potential can be derived from the oscillations in an aerial wire as 

 above described. In this manner I have constructed an arrange- 

 ment by which the ordinary feeble antenna oscillations can be 

 employed to ring a call-bell (see Fig. 18). The arrangement consti- 

 tutes an effective form of wireless electric bell. The operator can 

 then switch over the aerial to an ordinary valve receiving set and 

 listen to the telephone. 



The Marconi Company's engineers have worked out a type of 

 call-bell apparatus in which the " needle " or movable part of a 

 sensitive relay is made to close the circuit of a local battery and so 

 ring an electric bell. The peculiarity of this relay is that the 

 " needle " is not deflected sufficiently far to close contact by any 

 ordinary message signals, but only by a prolonged series of " dots " 



