ABSTRACT
The system of bells worked by the electric current, as illustrated in figures 668 to 671, consists of a battery, bell-pushes or pulls, and indicators connected by wires in such manner that a closed circuit may be formed at any time by pressing the push or using the pull. The electric bell is placed in some convenient position in the circuit and is supplied with two screw terminals with which to make connection with the wires. Electricity for lighting purposes may be obtained in many places from a central station, but it is frequently necessary and more economical in many establishments to generate electric current on the spot. In usual practice the lamps used for lighting purposes are the arc and the incandescent, the former being used for illuminating large areas and the latter for internal requirements. The direct current is preferable for the arc lights and also for motors.
