ADVANCES IN CARRIER TELEGRAPH TRANSMISSION 207 



circuits adjusted with 23 d.p.s. dots should be given a small initial 

 positive bias. 



It will be noted that the effective voltage available for charging the 

 condenser is not constant throughout the interval ab. The maximum 

 value which it can attain, and does attain if the signal is sufficiently 

 long, equals the effective charging voltage during steady marking; on 

 the other hand if the signal is very short, this value may never be 

 reached. It follows that the charge accumulated by the condenser 

 for any kind of intermittent signals is always less than that for steady 

 marking; the amount of the discrepancy depending on the wave shape 

 of the envelope. 



As a result of these effects, and other similar conditions which tend 

 to modify the average charge on the condenser depending on the 

 character of the received signals, there is a perceptible amount of /^ 

 characteristic distortion manifesting itself in a fortuitous manner during 

 the reception of ordinary text. 



The change in the mean condenser charge can easily be observed if 

 after a steady marking condition has been maintained for a few seconds, 

 dots are suddenly impressed on the circuit and their bias observed. 

 The latter will be found to drift as the charge assumes a new mean 

 value. In practice, an adjustment is made for this by observing the 

 change in voltage across the condenser under these two conditions and 

 adjusting the compensator-relay bias to maintain the drift within 

 limits which experience has shown to give minimum distortion with 

 ordinary text. 



Bibliography 



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Jan., 1926. 



3. Hamilton, B. P., Nyquist, H., Long, M, B,, and Phelps, W. A., "Voice Frequency 



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 1925, 



4. Nancarrow, F. E., "Line Telegraphy: More Voice Frequency Channels," 



Electrician, Vol. 122, p. 108, Jan, 27, 1939, 



5. Harrison, H. H., "Printing Telegraph Systems and Mechanisms," Lond., 



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6. Bell, J. H,, "Printing Telegraph Systems," A. I. E. E., Trans., Vol. 39, pp. 



167-230, 1920. 



7. Pierce, R. E., " Modern Practices in Private Wire Telegraph Service," A. I. E. E. 



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8. Gray, Elisha, "Nature's Miracles," Vol. 3, Electricity and Magnetism, pp. 126- 



128, N, Y., Fords, Howard and Hulbert. 1900. 



9. "II y a Cinquante ans: Essai du telegraphe harmonique de E. Gray," Rev. Gen. 



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