Page:Popular Science Monthly Volume 90.djvu/266

 250

��Popular Science Monthly

���Push-buttons installed in the upper and lower halls and in the bedrooms control the lamps, and the grounds can be flooded with light when burglars or tramps are prowling

��Making a Bungalow Unpopular with Night Prowlers

THE evil-doer loves darkness rather than light, so the Good Book says, and a Toledo man has found in the saying a sug- gestion for keeping tramps, burglars and chicken thieves away from his residence. The house is square and stands on a knoll, so when he installed a powerful nitrogen tungsten light in a reflector at each corner, the whole place presented a brilliant spectacle, not at all attractive to marauders. The lights are controlled by push-buttons inside the house.

��What a Circuit- Breaker Really Is

AN ordinary overload xA. circuit-breaker is merely an automatic electric switch which is operated by an electromagnet for opening the circuit whenever the cur- rent becomes dangerously high. Circuit-breakers are installed wherever large cur- rents are employed, and if it were not for them many powerhouses would be burn- ed up because of the tre- mendous currents that would develop from accidental short circuiting.

The accompanying illustra- tion shows a type of circuit- breaker that is now being used extensively in manufac-

��turing plants. It can be ad- justed to open a circuit at a certain maximum current. When such a point is reached, the current flowing through a copper coil will pull up the plunger. This strikes against the trigger and allows the operating springs to pull out the arm carrying the copper and carbon contacts. The carbons remain closed until the copper bridge is lifted from its contacts. The final break in the circuit there- fore is made by the carbons, and hence the formation of an arc on the copper is pre- vented. This not only pre- vents the copper bridge from becoming fused, but it also prevents the "copper from burning up. There are numerous other types of circuit-breakers serving many diff'erent purposes. There are under-load breakers for circuits that charge storage batteries, which open the circuit should the charging voltage drop and allow the batteries to dis- charge into the charging source; and there are others very much more elaborate in the, powerhouses themselves. Such are the distant-control breakers, for instance. Should any serious trouble occur the con- trol can be operated and the switch opened by a push-button.

���In this cir- cuit breaker a copper bridge is made to rise and open up the carbon contacts, the final break coming on the carbons

�� �