tdag Duplex Sgstem. 131 



throwing in the resistance, so that by this 

 means an ordinary Morse telegraphic relay 

 may be worked without ever entirely opening 

 the circuit. In the Way duplex system there 

 is a resistance at each station that is cut in 

 and out by the operation of its key, which 

 causes all the instruments in the line to work 

 simultaneously except the two harmonic relays 

 located one at each end of the line. These will 

 not respond to anything but the vibratory sig- 

 nal. 



In order to prevent the Morse relays at the 

 local offices from responding to the vibratory 

 current a condenser is connected around them. 

 Tin- condenser serves two purposes: It enables 

 the short impulses of the vibrating current to 

 pass around the relays without having to be 

 resisted by the coils of the magnets, and be- 

 tween the pulsations each condenser will dis- 

 charge through the relay at the local offices, 

 and thus fill in tho gap between the pulsations, 

 producing the effect on the relay of a steady 

 current. When a line is thus equipped it may 

 be treated in every respect as two separate 

 "f ili' ID doing way business and the 

 other through business. It is a curious blend- 

 ing of science and mech:ini-:n. 



her interesting application was made 

 of the system of transmission by musical tones 

 by Edison, some years ago. We refer to the 

 transmission of messages to and from a mov- 



