158 



Popular Science Monthly 



dimensions shown. The easiest way to 

 construct the pivot is to place the arma- 

 ture in the position it will occupy when 

 completed, and then drill a 1/16-in. hole 

 through both pieces and insert a piece 

 of steel rod of that size. The armature 

 itself is shown at K. This is of soft 



A — Detail of the break key base giving di- 

 mensions for the locations of the parts 



iron and can be attached to the armature 

 with one machine-screw. 



For supporting the contact-springs a 

 hard rubber crosspiece, L, is employed. 

 This is attached to the armature by a 

 machine-screw. Holes are drilled in it to 

 receive the machine-screws holding the 

 phosphor-bronze springs, M, in place. A 

 brass yoke is attached to the hard rubber 

 crosspiece G, and holds the setscrew for 

 adjusting the play of the armature. In 

 the large end is drilled a hole of such size 

 as to permit a 14/20 setscrew to pass with- 

 out touching. Four smaller holes in the 

 corners are used for attaching to the rubber 

 piece. 



A brass strip is bent to the shapes shown 

 at N and supports the contact-screws. 

 These are ordinary 8/32 brass screws. The 

 loop at the upper end of these supports 

 provides an automatic lock nut to prevent 

 the screws from turning when once set. 



For the contact-pieces 5/16 in. brass 

 rods with dimes soldered on the ends are 

 used. These are shown at O. If one is 

 willing to go to the expense he can have 

 silver plugs made by a jeweler, but in 

 actual practise it will be found that dimes, 



when filed smooth on the faces, will carry 

 all the current employed in most stations. 

 The shorter contact has a threaded stud 

 which screws into the armature. The other 

 one is made adjustable by means of a 

 setscrew in the hard rubber crosspiece. A 

 good way to get the dimes together in the 

 same plane is to set the brass shanks in 

 their proper places and clamp the two 

 dimes between them and then solder. On 

 separating the pieces it will be found that 

 they are in perfect alinement and meet 

 exactly when the key is in use. 



The various parts are assembled on a 

 wooden base of the dimensions shown at A. 

 Heavy binding-posts are mounted as shown 

 in the drawing of the completed instrument 

 and the connections from the moving 

 springs brought down to them by flexible 

 cord. The magnet-leads are brought to the 

 posts in the rear and the main break- 

 contacts to the side posts. The dotted 

 lines are the locations of the magnets and 

 pivot. For setscrews, fillister head brass 

 machine-screws, about 8/32 size may be 

 used. 



The connection with the other apparatus 

 is shown in B. The detector in this illustra- 

 tion is shown at D and should be placed as 

 close to the key as possible, since long 

 leads have induced in them currents that 

 are liable to throw the crystal out of 

 adjustment and make the break-in useless. 

 A battery of about ten volts should be used 



f9i 



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 J WWW L -h 



Key 



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B — The receiving tuner's primary is placed 

 the oscillation-transformer 



m series 



on the magnets. Less would be sufficient 

 but would not give the snappy action so 

 much desired. 



