646 THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1953 



is used, the teletype transmitting equipment common to all line insula- 

 tion test frames in a building is mounted in a separate 23-inch bay and 

 occupies about one-third of the vertical space. 



CONCLUSION 



The initial installation of the automatic hne insulation test equipment 

 in a No. 5 crossbar office has been in operation for more than a year and 

 the maintenance advantages of remote control of starting and automatic 

 testing and recording have been fully demonstrated. It is expected that 

 any future developments of line insulation test equipment undertaken 

 for other switching systems will follow this same general pattern. 



ACKNOWLEDGEMENT 



The authors gratefully acknowledge the assistance of R. C. Avery, 

 F. E. Blount and D. H. MacPherson in the preparation of the technical 

 descriptions and analyses presented in this paper. 



