. Cyclopedia of applied electricity : a practical guide for electricians, mechanics, engineers, students, telegraph and telephone operators, and all others interested in electricity . t controlling point 1 on the annunciator whicli causes --a A > r^ B © P® P(o) Fijj:. 17. the arrow to l)e turned and at the same time the bell rincrs. Afterthe attendant has noted the signal, the arrow is restored to itsnormal position by pressing a lever on the bottom of the annun-ciator box. The electric burglar alarm furnishes a very efficient protec-tion and is an application of the principles already
. Cyclopedia of applied electricity : a practical guide for electricians, mechanics, engineers, students, telegraph and telephone operators, and all others interested in electricity . t controlling point 1 on the annunciator whicli causes --a A > r^ B © P® P(o) Fijj:. 17. the arrow to l)e turned and at the same time the bell rincrs. Afterthe attendant has noted the signal, the arrow is restored to itsnormal position by pressing a lever on the bottom of the annun-ciator box. The electric burglar alarm furnishes a very efficient protec-tion and is an application of the principles already described. Thecircuit, instead of being completed by a push, is completed bycontacts placed on the doors or windows so that the opening ofeither will cause the bell to ring. The same device may be usedon money-drawers, safes, etc. In the case of the electric lire alarm, the signal iiiav l>e tjiveneither automatically when the temperature reaches a certain degree,or pushes may be placed in convenient locations to be operatedmanually. The pushes should be protected by glass so that theywill not be tampered with, it being necessary to break the glassto give the alarm. 230. THE ELECTRIC TELEGRAPH. Apparatus and the Horse Code. In order to get the beginners point of view, it is taken forgranted tiiat the reader knows nothing of electricity or the prac-tice of telegrapliy. If there is a shght knowledge of either ofthese, so much the better; but as a starting-point, we will con-sider that altogether familiar use of the electric current in theringing of a do(n--bell by pressing on a button. In so doing thenew arrival telegraphs the fact to the househohl, and asks foradmission, and those witliin respond to his message, althoughneither the one nor the other may know a dot from a simple combination of battery, wire and apparatus by whichthis action is carried on is as truly a telegraph ciicuit as is thelongest in tlie land, and a glance at its elements will serve as asteppi
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