LOCATION or OPENS IN TOLL TELEPHONE CABLES 



51 



made of the historical development of the art. The effectiveness of 

 the art was compared with the needs of present practices. 



2. Preliminary to the development of a suitable method, an analysis 

 was made of the errors which may enter into the determination of an 

 open location. These errors were classified for treatment or correction 

 during the development. 



Fig. 22 — 4-cycle motor-driven commutator with associated equipment. 



3. A mathematical analysis was made of the electrical characteristics 

 of the circuits on which open locations may be required. 



4. A suitable method was devised and an associated impedance 

 bridge circuit was developed which, in the light of the recent research, 

 most consistently and economically met the requirements for the 

 determination of open locations. 



After having completed an analysis of the problem and demonstrated 

 the practicability of the proposed methods, it remained to develop 

 applications of these methods for practical use. Equipment was 

 designed to develop a low frequency source of alternating j:)otential 



