Fig. 991.—Ceiling button. If a lamp be needed not more than 3 feet from the direct line of the wires, it can be hung where required by means of a ceiling button, as shown in the figure, but the lamp cord must not be used to run lamps in this way more than two or three feet from the rosette.
Ques. What provision should be made in wiring a hallway?
Ans. The switching arrangement should be so designed that the lights may be turned on or off either from the hall or floor above.
Ques. What is this arrangement called?
Ans. A two way switch, as shown in [fig. 992].
Ques. How can a two way switch be distinguished?
Ans. It has three binding screws, two on one end and one on the other.