Abstract: A control system for a light-generating apparatus can include a control cyclically operating a switching element in series with the circuit including the apparatus's power source and light. Upon actuation of the apparatus's switch within a specified switching interval, the control shifts to a drift mode causing the circuit to automatically pass through consecutive excitation states such that the light passes through successive levels of preferably increasing intensity at a rate independent of the switching interval over an adjustment interval of momentarily indefinite duration. Another switch actuation shifts to set mode, which stops the light at a desired intensity. The drift and set operations are repeatable. An indicator preferably enables the operator to adjust the light's intensity based on the available remaining life of the power source as differently determined for each different intensity.