Page:Popular Science Monthly Volume 89.djvu/962

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��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

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���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 the 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

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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.

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