| Knob | Tube |
| Flexible Conduit (BX) | Rigid Conduit |
In addition to the wiring for lighting there must be an independent system for bell service. The current for such a system must be supplied by dry batteries when the local power company gives a service of direct current, but when it supplies an alternating current a transformer can be used and the bells operated upon this energy. In the kitchen there should be a magnet-operated annunciator, connected with the front and rear doors and the dining-room push-button.
In laying out the lighting plans for a small house the standard symbols shown here are used, but a key should always be given to their meaning upon some part of the sheet, for it must be appreciated that the contractor can easily forget.
As an aid to laying out the lighting system on the plans, the following checking list is suggested, since it is simple.
SMALL HOUSE
ELECTRICAL EQUIPMENT LIST
Unless specified to the contrary, it is usual to assume that wall outlets in the living-room are to be placed 5 feet 6 inches above the floor, in bedrooms 5 feet 4 inches, and in halls 6 feet 3 inches. The usual height at which switches are placed is 4 feet.
Thus, by using common sense and the phrase in the specifications, “All work shall meet the requirements of the National Electric Code,” and requiring the contractor to furnish a certificate of approval for the entire installation as issued by the Board of Fire Underwriters having jurisdiction in the community, the architect has a reasonable surety of securing a good and safe system of wiring and lighting.