!)4S 



Popular Science Montlib/ 



A Dead End Switch of the Multiple- 

 Point Type 



DI'AD end switches usually bring to 

 mind the picture of a rotary disk 

 with some sort of puzzling springs and 

 contacts mounted around its edge. The 



KNOB 



CONTACT^ 



SirrrcH uver 



One of the contacts shown in detail 

 and the wiring diagram for the switch 



switch illustrated here is, to all appearances, 

 a regular multiple-point type, yet it is 

 doing all that any dead end switch can 

 possibly do. 



As will be seen the contacts fit into a 

 hole cut through the front of the case and 

 extend about 14 '"■ to the rear. The rear 

 end is soldered to a short spring-brass strip 

 that normally keeps it pushed outward, 

 the end of the strip making contact with a 

 small screw. The switch-lever should be 

 stiff and its edges curved to glide over the 

 points, moving them inward about ' s in- 



The parts arc attached to a board of in- 

 sulation, either wood, vulcanite, slate or 

 hard rubber; the wood, however, is easiest 

 covered. 



The operation will be apparent if you 

 keep in mind that the switch-Icvcr breaks 

 the circuit beyond each point on which it 

 rests. Thus, considering the hook-up, should 

 llu' lever be placcfl on point I, it 

 will push the spring out of contact with 

 tlic small screw, leaving coil A in the 

 circuit, yet breaking the connection to coil 

 B. This operation repeats itself all the way 

 aiound the contacts, the last one of which 

 recjuires no extra contact-screw. 



Such a switch may be mounted on llu' 

 secondary of a loose coupler and will 

 greatly increase the sharpness of the liming. 

 The extra contact-screws arc useful in 

 adjusting the distance the contacts extend 

 froni tlie front of the bci.ird. 



Making an Emergency Aerial 

 for Wireless 



IF there is a telephone line running into 

 the house and the aerial is down for 

 repairs, or for some other reason, fasten a 

 piece of tinfoil over the insulated wire of 

 the coiled telephone wires coming into the 

 house, then fasten the "lead-in" wire to 

 the tinfoil and connect the wire in the 

 usual way to the apparatus. This is a 

 practical stunt, and will not hinder the 

 working of the telephone. 



Intensifying Magnetic Fields for 

 an Automobile Dynamo 



IN the ordinary dynamo, the armature 

 moves between the poles of a number of 

 horseshoe magnets, usually arranged side 

 by side. In the illustration the magnets 

 are shown arranged in the usual manner, 

 namely, on opposite sides of the amiature, 

 with their similar poles in juxtaposition. 

 The drawings, for the sake of clearness and 

 simplicity, show only four magnets, al- 

 though as many as 32 can be used. 



The magnets are arranged with the four 

 south poles together on one side of the 

 armature, and the four north poles on the 

 other side. Such a disposal tends to 

 straighten the lines of force, thereby 

 intensifying the magnetic field in which 



A m :t'-od of magneto strengthening which 

 isfiniing much f.ivorwith ninnuf;icturcrs 



the armature m()\es. If the ojiposing mag- 

 nets .'ire fixed so that llieir poles UKU't on 

 the center line of the ann.ilure, the mag- 

 netic field will be imiforniK' (.listributetJ 

 around this ccnier line. 



