In 1984 the climber / inventor Paul Petzl came up with a headlamp with no on/off switch. To turn the light on or off, the housing around the lens of the lamp was rotated. Rotating this housing also served to focus the beam of light. This style of controlling lights is still seen in headlamps and flashlights. This design seems to be the precursor to the famous Maglite unless someone can show me that the Maglite was invented earlier. An advantage to this design is that the headlamp does not get turned on accidentally when the switch gets bumped in your pack.