MEASUREMENT OF TELEGRAPH TRANSMISSION 



169 



relay (Bias) through a network which modifies the wave-shape of the 

 signals and permits them to be biased easily by changing the current 

 through the auxiliary windings A and B of the Bias relay. 



The manner in which bias is produced will be understood more 

 fully by reference to Fig. 19 which shows graphs of the currents in the 



J 



(I) 



Fig. 19 — Currents in bias-producing circuit. 



bias-producing circuit. The current in the receiving relay input 

 circuit is indicated by 1. These are undistorted substantially square- 

 topped reversals. The currents flowing through the operating wind- 

 ings of the Bias relay in response to the marks and spaces of the re- 

 versals are shown by 2 and 3. In the case shown by 2, it is seen that at 

 the beginnings of the marking pulses the wave fronts are steep and that 

 the current gradually decays to zero at the beginnings of the spacing 



