﻿12 L. Sclivvendlor — On the general Theory of Dupleco Telegraphy, [No. 1, 



Further, if a relation between the resistances of one station has to hold 

 good between those of the other station also, the letters will be used without 

 any accents. 



The great practical advantage of the Bridge method, it will be clear at 

 once, is that any kind of receiving instrument which has been used for 

 single working may also be employed for Duplex Telegraphy. This fact 

 must always be of great consideration for any administration that contem- 

 plates the general introduction of Duplex Telegraphy. 



General expressions for the two functions " D" and " S." 



To obtain the functions D and S, we have first to develope the general 

 expressions for the forces p, P, and Q, say for station I. 



By ^' we understand the force which acts on the receiving instru- 

 ment g' of station I when that station is sending alone. (Station II at 

 rest.) 



p\ in our particular case, is therefore proportional to the current which 

 passes through the galvanometer in a Wheatstone's Bridge when balance is 

 not rigidly established, thus 



A' 

 P' « E' -j^ 



^^here A/ = a' d^ — b' (L/ + p") = a^ d/ — b/ c' 



and 



N' = g' (b' + d') (a' + c') -f f I g' (a' + b' + c' +d') +(c' + d') (a' + b') | 



+ a'c' (b' + d') -f- b'd' (a' + cO 



Further, by P ' is understood the force which acts on the receiving 

 instrument in station I, when station II is sending alone : Single Signals. 



This force in our particular case is proportional to the current which 

 passes through the receiving instrument of station I when station II is 

 sending alone, and we have consequently 



P^ a CVf 



where C" is the current which enters the line at point 2, when station 

 II alone is sending; C" fx,' the part of this current C" which arrives 

 actually at point 1 (on account of leakage between points 2 and 1, a part 

 of C" is lost), and C" fj.' xb' that part of the current C" fc^ which ultimately 

 produces the signal (single signal) in station I. The current C" fi' arriving 

 at point 1 branches off in two, one part goes through a' and the other 

 through g' to earth. 



Further 



where 





C'^ 



--"W' 











.-. P 



'-^"i^ 



'■A 



/ 





ni* 



= S" (b" 



+ d") + d" 



(a" 



+ 



h') 



