62 



METHODS OF COMMUNICATION FOR FOREST PROTECTION 



set upright and held in place by two nuts N, one on each side of the arm. Care must be 

 taken to see that these standards do not project below the arms more than the thick- 

 ness of the lower nut. The portion threaded should equal the thickness of the arm 

 plus the thickness of the two nuts. The cost of the whole apparatus is so small that 

 after the iron fittings are removed' the rest may be discarded, if necessary, when the 

 work is completed. 



No more wire should be strung out than can be put up and tied in during one day. 

 Special care should be taken not to allow the wire to lie across trails or roads where 

 it might be run over by vehicles or trampled by animals. Kinks or nicks made in 

 this way may weaken the wire sufficiently to cause it to break as soon as a little 

 strain is put upon it, or when it contracts in cold weather. All kinks should be 

 straightened before the wire is stretched. If the kinks or nicks are bad' they should 

 be cut out and a splice made. 



5 TRANSPOSING LINES 



By transposition is meant changing the lo'cation of a wire from one side of the. 

 pole to the other (Fig. 21). This is 1 done to overcome the effects of outside inter- 

 ference existing in lines which are close to or parallel with high-tension transmission 

 lines, and wires which are on poles carrying other wires-. 



Brace of brocket 

 on reverse s/c/e 

 ofsorne /eve/ 



ELEV/3T/OM 



PL/? A/ 



Fig. 21 Transposition of wires, metallic circuit 



When building a metallic circuit, the wires should be transposed once every mile. 

 Where the line is exposed to induction, cross-talk, power wires or electric-light wires, 

 the line wires should be transposed at least every tenth pole. In transposing telephone 

 lines, the wire on the left should always cross over, never under, the wire on the right, 

 and without touching it. On a bracket line the transposition can be made very easily 

 by changing the location of the brackets on the pole, as shown by the upper diagram in 

 Fig. 21. When a cross-arm is used, transpositions can best be made by using a standard 

 two-piece transposition insulator. Transpositions should be arranged for at the time 

 the wire is unreeled; the left-hand wire crossing over on top of the right at the point 

 where the line is to be transposed. 



6 SAG ALLOWANCE 



The stresses in the telephone wire undergo changes with variations in temperature, 

 thus making it necessary to provide for the extreme variations in wire length in each 



