Patent ID: 8159146

Claim:
An apparatus comprising: at least one light-emitting diode (LED); a DC voltage source that has an amount of electrical power; a pulse-controller circuit operatively coupled to the voltage source and to the at least one LED that: in a constant-light-output-characteristic mode, withdraws pulsed current from the DC voltage source and supplies power from the withdrawn pulsed current to the at least one LED such that a characteristic of light output from the at least one LED remains substantially constant as the amount of electrical power remaining of the DC voltage source varies over a range that would otherwise change the light-output characteristic of the at least one LED, and in a power-indication mode, controls at least one visibly perceptible light-output characteristic of the at least one LED such that the at least one visibly perceptible light-output characteristic provides an indication to a human user of a remaining portion of the amount of electrical power.