How to Install Electric Bells, Annunciators, and Alarms. / Including Batteries, Wires and Wiring, Circuits, Pushes, Bells, Burglar Alarms, High and Low Water Alarms, Fire Alarms, Thermostats, Annunciators, and the Location and Remedying of Troubles

by Norman H. Schneider

Fire Alarm Circuits.

A fire alarm circuit suitable for factories, private plants or groups of buildings is shown in [Fig. 68]. It is a series system, with closed circuit, the gongs sounding whenever the circuit is opened whether by the contact breaker in the boxes or by the accidental breaking of a wire. This insures that it remains in good working order, as when any part of the circuit is opened, a warning tap is sounded on every bell or gong.

The boxes have contact breakers which send a separate number of impulses for each box, thus announcing the box number on each gong. The boxes and gongs may be located anywhere, as the system is perfectly flexible.

The reference letters in the diagram are as follows: C indicates the gongs which are preferably of the electro-mechanical type, a coiled spring providing force for the blow, electricity being merely used to release and retain the hammer or striker. The alarm boxes are marked BB and the battery which is of the closed circuit type is marked D.

Fig. 68