KENNELLY AND UPSON— HUMMING TELEPHONE. 



363 



tions of reinforcement will permit. If a lower tone, with a phase 

 lag e more than 270°, will give more amplitude than the higher note 

 to which it has been driven, with 6 less than 270°, it will break 

 pitch downwards. This process will continue down to the first 

 wave-length of tube, or 40 cm. in the case examined. For connec- 

 tion / of the receiver, it can break to no lower note after passing 

 270°, and the tone will rise to such a pitch that the amplitude be- 

 comes insufficient to excite the transmitter, so that silence should 

 ensue at or near the length 12 cm., as actually observed in Fig. 3. 

 The curve / of frequency between 12 and 50 cm. accords fairly well 

 with the curve y = 1,000 in Fig. 17. 



Fig. 18. Fig. 19. 



Fig. 18. Diagram of Electrical Connections with Step-up Induction Coil. 

 Fig. 19. Equivalent Diagram of Connections, with Level Induction Coil. 





R 1-i^-t.Jul 0.0013277 /«g« "'ycx 0.00171. 



'w&L^ 



Fig. 20. 



Fig. 21. 



Figs. 20 and 21. Equivalent Conductive Connections with Level Induction 

 Coil and Alternating E.]\I.F. 



With reference to the influence of capacity in the secondary cir- 

 cuit. Figs. 18 to 21 show the successive steps by w^hich the secondary 

 circuit may be treated as a conductive branch of the primary circuit. 

 Using the constants given in Table I., ignoring any capacity exist- 

 ing between the windings of the coils, and assuming that the effect 

 of the transmitter in the primary circuit is equivalent to an alter- 

 nating e.m.f. e, working through a transmitter resistance R, of 50 

 ohms, we find a coupling coefficient for the coil of i^ = 0.937, ^^^ 



