NEGATIVE IMPEDANCE TELEPHONE REPEATERS 



1087 



Fig. 25 — Test set showing repeaters and test cords. 



the current to a new value h . The ratio of the currents h/Io is a direct 

 measure of insertion gain or loss between Zi and Z2 due to inserting the 

 network. The db change in transmission caused by the insertion of N is 



Insertion transmission in db = 20 logio y~ • 



Jo 



\\'lien 7i is less than /o , the addition of A^ has caused an insertion loss, 

 and when h is greater than h the addition of .V has caused an insertion 

 gain. In the test set the current indicating device has a db scale so that 

 the change in transmission can be read directly in db. 



TRANSMISSION MEASUREMENTS 



In setting up to make repeater tests, the E2 and E3 units are removed 

 from their shelf positions and plugged into adapters in the test set, as 

 showni in Fig. 25. A test plug, fashioned to simulate the male connector 



