INSTALLATION OF TEMPORARY EQUIPMENT 113 



only painful but might be dangerous to the ear. 'Special precautions must always be 

 taken to make sure that the line is not in use before attempting to call a station with 

 this hand set. 



The aluminium case is thin, and dents or other injuries which it might receive 

 from rough handling can easily form contacts that may destroy the usefulness of the 

 set. These must be carefully avoided and the sets must always be transported in the 

 leather cases furnished with them. These cases are made large enough to hold the 

 necessary connectors and a folding ground rod. 



m 



Fig 1 . 66 Forest officer preparing to use the Adams hand set with 

 Cree knife for ground rod 



3 BUZZER SIGNALLING 



The vibratory currents produced by the Adams hand set are of very high-tension 

 and will traverse lines that are in such poor condition that bell signals will not pass 

 over them. It is therefore feasible, when lines for any reason are in extremely poor 

 condition, to call stations with this set at much greater distances than with the bells. 

 It is even possible to signal across breaks in the wire providing the ends of the broken 

 wire make a good ground contact, preferably with moist earth. In this case, however, 

 signals cannot be heard in the howler but can only be heard in a receiver held to the 

 ear, which restricts the practical utility of this capacity to those few forests that 

 maintain permanent telephone operators with head receivers. Tests have shown that 

 signals are plainly transmitted across a 65-ft. gap and may be distinguished very 

 faintly across a 210-ft. gap. They will also traverse miles of bare iron wire lying 

 on the ground, even in wet weather, and at a distance of one mile may be heard in the 

 howler. The sound produced in an ordinary receiver at a distance of 50 miles over 

 very poor lines can be heard several rods away. At a distance of 200 miles over lines 

 too poor for transmission of speech, signals are plainly audible in the receiver when 

 held to the ear. and weakly audible in the howler. 



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