An electrically operated equipment with a sealed enclosure containing circuitry with an exterior visual indicator to show a state of operation of the equipment. The visual indicator is illuminated by a magnetic flux sensor also exterior to the equipment, the sensor inducing an electrical current from a sensed magnetic flux passing through a permeable wall of the enclosure. The magnetic flux is provided by a magnetic field generator within the enclosure. The generator is connected to the equipment to generate the field when the circuitry is operating correctly whereby the indicator shows a correct state of operation. The invention avoids the use of sealed orifices in the enclosure for conductors to pass to exterior LEDs or LEDs sealed within the enclosure and possible resultant leakage. The invention is useful for optical network units. The invention also includes a visual indicating device of multi-layer configuration and a method of visually indicating the operational state of circuitry.