Page:Incandescent electric lighting- A practical description of the Edison system.djvu/67

 without them as, when the circuit is properly balanced, no current passes over these wires, la addition to the equalizers the positive and negative feeders are supplied with am-meters so as to guide the attendant in regulating the current in each, and all have "Safety-catches" composed of strips of a metal melting at a very low temperature.

Any excess of current passing over the line of feeders, either to or from the station, will melt these safety-catches before any damage can be done either to the lamps outside or to the apparatus within the station.

The number of lights in operation upon a circuit varies at different hours, and this variation must be provided for; that is, only enough current should be generated to supply the lights in actual operation.

It would be far from economical to run a station up to its full capacity throughout the time when lamps are burning, as different classes of buildings require light in different measures, and while some