A smart card includes a first circuit delivering a power supply voltage and a second circuit coupled to the first circuit by an electrical conductor and powered with the power supply voltage. A light-emitting diode has a first terminal coupled to the electrical conductor and a second terminal coupled to a first terminal of the second circuit. During a first operating phase, the first circuit delivers a first value of the power supply voltage and the second circuit applies a first voltage to the first terminal. During a second operating phase, the first circuit delivers a second value of the power supply voltage and the second circuit applies a second voltage to the first terminal.