CHAPTER V. 



CONSIDERATIONS OF THE TELEPHONE AND 

 TELEGRAPH LINES AND THEIR INFLUENCE 

 ON PHOTO-TELEGRAPHY. 



As the two qualities, leakance and resistance, of 

 the lines connecting two photo -telegraphic instru- 

 ments have a final influence on the limits of long- 

 distance transmissions, and the capacity and in- 

 ductance factors have a large influence on the 

 quality of the pictures and the rate, etc., with which 

 they can be transmitted, some short discussion of 

 the matter becomes necessary. 



The actual effect of capacity is, as has been 

 pointed out elsewhere, a lengthening of the dura- 

 tion of the current, but we shall now see how these 

 effects can be experimentally demonstrated. A 

 modified form of the Einthoven, or string galva- 

 nometer, was employed to record photographically 

 the effects of capacity on the currents transmitted 

 through a high -resistance line by the transmitter, 

 as used in the telautograph and telectrograph. The 

 arrangement is seen in Fig. 51. A band of 

 sensitive film MOQ travels over rollers in a light- 

 tight box, being actuated by a well - regulated 



