One of the desirable features of early liquid fuel and gas lamps was the ability to adjust the light intensity. However, Edison also incorporated the ability to change the light level in a lamp although it was done in an inefficient manner. Occasionally one will find such a lamp and it can be identified by a turn screw at the upper end of the base near the bulb. When one turned the screw a resistance was added in series with the carbon filament. Later this feature of light level adjustment was pursued by Hylo as well as Economical and the following comments describe the types of lamps available in 1910.

It was very difficult to manufacture a carbon filament rated at 1/2 or one candlepower at the normal voltage of 110 volts; therefore two filaments were connected in series. The potential drop over the larger filament was about 20% of the voltage impressed on the lamp. The ratio of the power (watts) consumed on the high brightness step relative to the low brightness one was about six to one. The high brightness level was obtained by means of a switch that either short-circuited or open-circuited the smaller filament.

One lamp type that was available was the Pull String Economical. In that lamp the switch was mounted on the outside of the base and a draw string looped through it. The lamp could be identified by round discs located at the ends of the string. One disc read "BRIGHT" and the other, "DIM". The switch was rotated slightly by the strings. When both filaments were in series only the dim filament was lighted.

Another turn-down lamp type was the Pull String Hylo. In that lamp the switch was concealed in the base. A drawstring entered and exited the base through two small holes. This lamp was designed to give 16, or one candlepower, as well as an off position. Again, when both filaments were in series only the smaller filament gave light.

A third design was the Turn Bulb Hylo. In that design there was a spring contact located on the end base contact. When the bulb was first turned into the socket the low light level came on. Upon further turning of the lamp the higher light level came on. Again, on the low level both filaments were in series whereas on the high light level the small filament was short-circuited.

A fourth design was the Economical Turn Bulb. It had a sliding spring collar on the base. It slid over a contact when the bulb was turned.

Another design was known as the Long Distance Lamp. It was controlled by a small pull chain switch or a lever switch, which was attached to a triple wired cord. The cord was attached to the lamp by three clamps or three thumb screws. This lamp could give a high or low light level or an "off" position.

All the previous designs employed carbon filaments. In those designs the available light level combinations were: 8 and 1/2 c.p.; 16 and 1 c.p.; 32 and 1 c.p. In 1910 there was also a MAZDA Pull String Hylo that employed a sintered tungsten high light level filament and a smaller carbon filament. It was furnished in only one size, 35 watts, 27 c.p. (high level) and 1 c.p. (low level) for voltages 100 to 130 volts.