Turn-down lamps of the latter form are made in several styles, the chief points of difference being in the method of changing the contact from the high-to the low-power filament. In Fig. 222 a sectional view shows the “pull-string” form of lamp in which the parts are exposed. The long filament _H_ and the smaller one _L_ represent two individual lamps of different lighting power. The change in light is made from one to the other by pulling the string which is attached to a switch in the socket and which changes the contact to send the current through the filament giving the desired amount of light. The figure shows a carbon-filament lamp, but tungsten lamps are made to accomplish the same purpose. The difficulty of manufacturing a 1-candlepower tungsten lamp for direct operation on a 110-volt circuit requires the filaments to work in series. The figure is arranged on the same plan as for a tungsten lamp. The lamp base when screwed into the socket makes contact with the two service wires of the circuit at _A_ and at _E_, which are part of the screw base. To light the lamp the current is switched on as in any lamp. The current enters at _A_ and passes down the connecting piece to the contact _B_. The piece _B_ is moved by the cord to light either the large or the small filament. In the position shown the current enters the small filament at _C_ and in order to complete the circuit to _E_ must traverse both the large and the small filament. The resistance of the small filament is such that the passing current raises it to a temperature of incandescence but the large filament does not heat sufficiently to give an appreciable amount of light. When the cord is pulled to light the large filament, the contact is made at _D_ and the current passes directly through the large filament to complete the circuit at _E_. Turn-down lamps are especially adapted to the home. Their use in a child’s bedroom or sick chamber is a great convenience. The lamps are often constructed with a long-distance cord extending from a fixture to the bedside. By this means a dim or bright light is given as desired, with the least inconvenience. Turn-down lamps are made in a variety of sizes. The large filaments are arranged to give 8, 16, and 32 candlepower. With the 8-candlepower lamp the small filament gives 1/2 candlepower and with the 16-and 32-candlepower the small filament gives 1 candlepower. With the lamps described, the variation in amount of light is attained by changing the contacts, to bring into action filaments of different resistances. They admit of only two changes, either the lamp burns at full capacity or at the least light the lamp will give. The heat liberated by the large filament, when the small light is in use, takes place inside the lamp globe.