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An Automatic Pressure-Gage Alarm 



AN ordinary pressure-gage may be 

 easily equipped with a simple 

 home-made contact device, which will 

 serve as an automatic alarm, giving the 

 attendant an audible signal, when the 

 pressure has exceeded or dropped be- 



Popular Science Monthly 



Diagram of connections for making an 

 audible pressure-gage alarm 



low a previously determined value. This 

 device may be arranged as follows: 

 Carefully remove the glass front of the 

 gage and also the needle from its 

 spindle. Then, on the under side and at 

 the outer end of the pointed end of the 

 needle, fasten a very light piece of 

 spring brass, which is to brush over the 

 contact to be mounted on the face of the 

 dial. This contact is fastened on the 

 face (of dial) in such a position that 

 the spring on the end of the needle is 

 in perfect contact with it, when the 

 needle indicates a pressure correspond- 

 ing to the value at which the alarm ^ is 

 to be given. It is, of course, to be in- 

 sulated from the dial, and in turn, con- 

 nected to a binding post, mounted on the 

 outside of the frame, or containing case, 



of the pressure-gage and properly in- 

 sulated from it. A second binding post 

 is mounted on the case itself, and elec- 

 trically connected with it. These two 

 posts form the contact device, and are 

 connected in series with the bell battery 

 and a small single-pole switch. In re- 

 mounting the needle on its shaft, great 

 care must be exercised to see that it oc- 

 cupies the same position on the face of 

 the dial that it did before. A little error 

 may prove of great damage, in case it 

 should indicate a pound or so less than 

 is really the actual pressure. The spring 

 of brass, on the outer end of the needle, 

 should be very light and flexible, and so 

 adjusted that it will move over the con- 

 tact on the face of the dial with the 

 minimum friction. It would, no doubt, 

 be best to fasten a small piece of plat- 

 inum on the points that touch or coincide 

 with each other, to prevent trouble due 

 to corrosion and arcing. 



A diagrammatic sketch of the entire 

 device, including the electrical connec- 

 tions, is presented herewith. One or 

 more additional contacts may be mount- 

 ed on the dial, at various spaces show- 

 ing different pressures, etc. These con- 

 tacts may also be put in circuit with 

 bells, buzzers, and the like with different 

 tones. — Wm. Warnecke, Jr. 



Fools Automobile Thieves 



PROBABLY the simplest way to dis- 

 appoint the automobile thief is by 

 means of an inconspicuous lock which 

 short-circuits the ignition system. Two 

 springs should be installed in the walls 

 of a rubber tube. When a rubber plug 



5pnna. 



A'short-circuit of the ignition system is the 

 safest guard against automobile thieves 



is inserted, the springs are forced apart 

 and the current will go to the spark- 

 plugs as usual. Withdrawing the plug 

 allows the springs to come within 

 sparking distance of each other, and the 

 circuit is temporarily put out of order. 

 One spring should be connected to the 

 terminal of the magneto and the other to 

 the automobile frame. 



