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HANDBOOK OF PROJECTION FOR
in the house. Attach one side of the button to upper wire and the other side to the battery wire, as shown. In the illustration we see four batteries connected in series. This being a fire alarm system, it is desired that the bell or buzzers ring very loudly, hence several batteries are connected in series. Employees should be made to understand that it will mean instant dismissal to ring these bells, except in case of actual necessity. The system can be arranged for any number of bells, from one to a dozen, and there can be as many push-buttons as desired.
Fig. 371 illustrates the method of connecting a bell so that it may be rung by more than one button. By this plan as many buttons may be installed as desired, any one of which
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Figure 373.
will ring the bell, provided the wire from push-button to battery wire be not connected between battery and bell. A-A-A are push-buttons.
In Fig. 372 we see the method of wiring an ordinary annunciator. The plan is too plainly shown to require explanation. The buttons may, of course, be located anywhere in the building, and ordinarily are widely separated.
ELECTRIC PROGRAMME BOARD.— Fig. 373 is the wiring diagram of an electric programme board. I think the action will be plain when you trace through the contacts in Fig. 373.
Wire A, we may call the permanent connection. As you will observe, it connects directly to one side of all the lamps. Wire B connects through switch C and movable arm D to the various contacts 1, 2, 3, 4, etc. Now suppose we