TELEPHONES 



455 



Line construction. The kind and size of wire to be used 

 for the line will depend upon the length of line, the system 

 of battery supply, the number of stations, and the system 

 of signaling. It will usually be found, however, that satis- 

 factory private lines can be constructed by use of No. 12 

 BWG iron wire for lines up to ten miles in length, and No. 9 

 BWG iron wire for lines up to twenty-five miles in length. 

 A competent telephone engineer can advantageously be called 

 in for the consideration of this question. A good grade of 

 galvanizing should be insisted upon. 



A test for galvanizing is as follows : Prepare a saturated 

 solution of copper sulphate. Dip a sample of the galvanized 

 wire to be tested into this solution, and leave it for one 

 minute, then take the sample out and wipe it clean. Repeat 

 these operations four times. If the sample has a copper 

 color, the galvanizing is too thin and the material should 

 not be considered acceptable for telephone line wire. If 

 it is black in color, it is satisfactory. 



As to supports for the line wire, wood poles are recom- 

 mended. They may* be 

 of cedar, chestnut, pine, 

 tamarack, or cypress. 

 They should be not less 

 than 5 inches in diam- 

 eter at the top, and 

 should be of sufficient 

 length to insure sup- 

 porting the wires the 

 height required by the 

 regulations of the gov- 

 erning bodies having 

 jurisdiction over any of 

 the territory through FlG - 348. Pole with brackets 



which the line passes. Outside the limits of incorporated 

 villages, 20-foot and 22-foot poles are frequently used. 

 Thirty-two poles to the mile is considered good practice. 



60D. 



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