Popular Science Monthly 



79' 



Testing Electric Wires for High 

 Tension Currents 



MEN who work on high tension lines of 

 electric service must be certain that 

 the current is turned off from them. As an 

 added precaution against the accidental 

 throwing of the wrong switch they should 

 securely ground the circuit until work 

 on it is finished. Several types of more 

 or less efficient "high tension" testers have 

 been put on the market and most of these 

 have been either of the "gold leaf" electro- 

 scope or the more expensive quadrant 

 types. All of these give negative results, 

 because if they do not indicate the presence 

 of high tension voltage, one of two condi- 

 tions may exist. Either there is no current 

 in the wire being tested, or the instrument 

 does not work perfectly. In the first case 

 the workman is safe, but in the second 

 case, if he relies on the indications of his 

 electroscope his life may be forfeited. 



We are not willing to recommend as safe 

 any of the electrostatic types of voltage 

 indicators unless they can be positively 

 checked immediately before and after the 

 proposed observation. I have handled 

 high tension circuits for years and find that 

 a person can make an electroscope for 

 testing the presence of high voltage with no 

 apparatus. This may sound paradoxical, 



but I use a very fine silk thread pulled from 

 my necktie. If this fiber is sufficiently fine 

 and is held by one end so that the other 

 shall be very close to a high voltage line the 

 free and finest end of this silk fiber will 

 pulsate with the variations in an alternating 

 current. 



In close proximity to a high tension direct 



current wire the free end of the fine fiber 

 will be attracted toward it. If allowed to 

 touch it, it will become charged and will be 

 instantly repelled. Close and caieful 

 observation is necessary in the use of so 

 simple a device. It cannot be depended 

 upon to work in the wind or rain, but as an 

 emergency electroscope it may help some 

 reader. However, we advise a workman to 

 check results on a circuit known to be 

 carrying high voltage and — results or no 

 results — play safe. — T. B. Lambert. 



Resistance in Circuit to Make 

 Double Tone Automobile Horn 



WITH a small amount of resistance 

 placed in the circuit leading to an 

 automobile horn or other electric signal 

 the tone may be lowered 

 to some extent, the number 



Changing the tone of a horn with a double 

 contact push-button with resistance in one line 



of sound waves being reduced to the 

 amount of resistance used. 



A simple way to work out this problem 

 is to make a double contact push-button, 

 which is clearly shown in the diagram. 

 About 3 ft. of No. 20-gage German silver 

 wire will be about right for the average 

 electric signal such as used on automobiles 

 and motorboats. 



A very convenient place for the resistance 

 can be made by cutting a groove around the 

 base of the push-button. When the button 

 is pressed slightly the signal will sound 

 half-tone. Pushing the button all the way 

 down will cause the full tone to be pro- 

 duced. — Howard W. Peacock. 



A Strong Guy-Wire Anchor for 

 Aerial Poles 



NO mast is stronger than its weakest 

 guying part, whether that be the guy- 

 wire or the anchor. Only recently an 

 amateur's 6o-ft. mast was broken to pieces 

 in a 45-miles-an-hour gale because one of 

 his guy-posts gave way. In this case the 

 amateur used a 3-ft. length of 2 by 4-in. 

 material driven in all but a few inches into 

 the ground. This was easily uprooted by 



