1920] Thermionic Valve in Wireless Telegraphy & Telephony 181 



generators to transmit articulate speech across the Atlantic during 

 daylight hours. These experiments were conducted between Bally- 

 bunion, Co. Kerry, Ireland, and Louisberg, Cape Breton, Nova 

 Scotia. The engineers in charge responsible for the design and 

 working of the stations were Mr. W. T. Ditcham in Ireland and 

 Mr. W. J. K. Picken in Nova Scotia. The tests lasted over 10 or 12 

 days, and were all carried out between 10 a.m. and 1 p.m. Gr.M.T. 

 The distance separating the stations is 1800 miles. 



The aerial wire was of umbrella form, supported on masts 

 500 feet high. The transmitting plant consisted of two three- 

 electrode generating valves, with a third control valve for speech 

 modulation. A small alternator of 2*5 kilowatt power supplied an 

 alternating current which was stepped up in potential to 12,000 

 volts and rectified by a two-electrode or Fleming valve. The con- 

 tinuous waves generated had a wave length of 3800 metres, or nearly 

 2| miles. The receiving appliance comprised a multiple valve 

 detector with valves in cascade. The external appearance is as shown 

 in Fig. 16, and the connections as shown in Fig. 10. 



The reception was by a series of six valves in cascade, with a final 

 detector valve. The speech transmission was perfectly good and 

 clear across the Atlantic, and so loud at Chelmsford, 500 miles away 

 from Ballybunion, that it could be heard on a simple frame aerial. 

 There was nothing of the nature of freak transmisssion, but for 

 regular working at all times experience showed that rather more 

 power will be required. A battery of half-a-dozen generator valves 

 of the type used, and now exhibited here, will probably be sufficient 

 to give a regular service of trans-atlantic radio-telephony. 



Before leaving the subject of radio-telephony it may be remarked 

 that, both in connection with it and with the every-day uses of radio- 

 telegraphy in maritime intercommunication, there is a great demand 

 for an effective wireless bell call. On board ship where a message or 

 even an S.O.S. signal may come in at any moment, the operator on 

 duty has to sit with the telephones to his ears, held there by a steel 

 head-spring. 



Ever since the terrible tragedy of the s.s. " Titanic " it has been 

 the custom for large ships to carry two operators, who take wireless 

 duty in turn, but in small ships where only one operator is carried 

 the duties may become very onerous, or some important call may be 

 missed. 



In ordinary exchange telephony we call up the exchange or a 

 subscriber by ringing an electric bell. To do this, however, requires 

 more power than can be supplied directly from the receiving aerial. 

 Some sensitive form of relay has to be employed in which the aerial 

 current closes the circuit of a local battery, and this supplies a current 

 which rings a bell. In wireless work, however, certain conditions 

 have to be fulfilled. It is essential that the relay should not be put 

 in action by every passing electric wave, or dot-and-dash message 



