Multiple Eransmfealon. 



117 



The divided current does not affect A's own 

 station, being neutralized by the differential 

 magnet, but it does affect B, whose instrument 

 responds and gives him the message. 



Now B may at the same time send a message 

 to A by half of his own divided current from 

 his own end of the line. 



The puzzle to most people is : How can the 



500 MILES 



Represents a duplex 500-mile telej?raph-Hne. A and B are 

 the two terminal nations; B B', the batteries; KK', the keys; 

 D D'. the small resistance -oils, -qual to the battery-resist 

 ance when the latter is not in circuit: R R , resistances each 

 equal to the 500-mile line; and C C', condensers Riving the 

 artificial lines B R' the same capacity as the 500-mile line. 



signals pass each other in different directions 

 mi the same wire? But the signals do not have 

 to pass each other. Tn effect, they pass; but 

 in fact, it is like going round a circle the 

 earth forming half. A sends his message over 

 the line to B. "B sends his message to A 

 through the eartli and up A's ground-wire. 

 Tin- operative \vli -ling with positive 



pole to line pushes his current through so to 



