Abstract: An optical indicator for industrial use comprises an elongate hollow casing with at least two partially transparent longitudinal bands and houses a support structure carrying at least two bulbs in correspondence with the bands and connected to electrical terminals at one end of the support structure. At least one electrical connector is coupled to the said end of the bulb-holder structure and is fixed in a first end of the casing. The bulb-holder structure is mounted in the casing so as to be removable through a second, open end of the casing and a closure member is fixed to the end of the structure opposite the connector. The closure member is adapted to be coupled to the second end of the casing with mutual lateral covering over a predetermined axial length such that, when the bulb-holder structure is removed from the casing, it is disconnected from the connector before the closure member is disconnected from the casing to an extent sufficient to allow access to the interior of the casing.