Suppose that you intend to use three 6 volt 12 candlepower lamps. Each lamp will require two amperes or a total of six when all three lamps are burning at the same time. Six amperes multiplied by eight ampere hours equals 48 ampere hours. This is the smallest size of battery which should be used. If it is larger, it will be advantageous, because it will supply the lamps a correspondingly longer time without recharging. Figure 155 shows some of the sockets or receptacles which are on the market. The illustration to the left is a "flat base receptacle." It will be found most useful when the lamp is to be mounted directly on the wall or ceiling. The weatherproof type of socket may be secured with either a fibre or a porcelain shell. [Illustration: FIG. 158.—A Tungsten Automobile Lamp with Ediswan Base.] The brass shell socket is the best wherever appearance counts. It is patterned after the standard Edison sockets and is made so that it will screw onto several different sizes and styles of brackets which may be mounted on either the ceiling or the wall. This type of socket is also made with a small switch built inside so that the lamp may be turned on or off directly at the socket. *The Wire* used to connect the system will depend upon where the lamps are located. Annunciator or office wire as it is sometimes called will serve in most cases where the wires are to be run entirely indoors. The largest size made is No. 16 B. & S. Gauge. This is the size which should be used. Annunciator wire is made in various colors so that it can be more easily concealed. If the wires are run outdoors, or somewhat exposed to the weather, as on a porch or in a barn, it is advisable to use weatherproof or rubber covered wire. Lead covered twin conductor is recommended for use aboard boats or wherever the wire is liable to abrasion. [Illustration: FIG. 159.—Lamps Controlled by One Switch.] If the lamps are larger than eight candle-power, or several are to be used on the same line, the wires should be larger than No. 16. When a battery is connected to a system of wires, the voltage at the end of the line is much lower than it is at the battery terminals. This is due to the resistance of the wire and is called "voltage drop." The lamps at the end of the line will not burn as brilliantly as those close to the battery. This can be partially overcome by using large wire. The lamps may be either connected in series or in multiple. When a six volt battery is used, it will be necessary to connect them in multiple. Figure 159 shows how several lamps may be connected in multiple and controlled by one switch. Figure 160 shows the same lamps with three separate switches so that each lamp may be turned on or off individually. [Illustration: FIG. 160.—Lamps Controlled by Separate switches.]