168 



THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1957 



Fig. 2 — Parts used in the stem and a finished stem of the 175HQ tube. The 

 separate beading of the leads maj' be noted. 



periodic observations of repeater performance indicate no statistically 

 significant change in tube performance over the 6 years of operation. 



Sufficient tubes were made at the same time as the Key West-Havana 

 run to provide the necessary tubes for a future transatlantic cable. These 

 tubes were never used principally because the tubes had been assembled 

 with tin plated leads. Tin plating, subsequent to the laying of the Key 

 West-Havana cable, was found to be capable of growing "whiskers".^ 



In 1953 another production setup was made, also in Bell Telephone 

 Laboratories, for the fabrication of tubes for the Newfoundland-Scotland 

 section of the transatlantic cable. On the completion of this job fabrica- 

 tion was continued to provide tubes for an Alaskan cable between Port 

 Angeles, Washington, and Ketchikan, Alaska. After a pause of several 

 months another run was made to provide tubes for a cable to be laid 

 between California and the Hawaiian Islands. 



Mechanical Features 



The tube, shown on the left in Fig. 1, is supported in the repeater 

 housing by two soft rubber bushings into which the projections of the 

 two ceramic end caps fit. All leads are flexible and made of stranded 

 beryllium copper which has been gold plated before braiding. Both for 



