Abstract: Liquid level indicator in a tank of the type having a total-reflection optical sensor (1). The sensor is mobile vertically, so as to be able to be immersed or partially immersed in relation to the liquid level. The optical sensor (1) has an integrated light transmitter (DE) and receiver (PR) and is suspended by a non-extensible cable (5) wound onto an upper drum (6), the drum being driven upwards or downwards by a stepping motor (9) relative to the liquid level. The sensor (1) is connected with a wire (10) through a pully (13) ballasted with a weight (14) and fastened at its upper end so as to provide both the mechanical tension of the cable (5) and the electrical connection of the mobile sensor (1). The indicator also comprises a magnetic sensor (16) co-operating with a magnet (17), one of these two units being fixed in the top position and the others being mobile with the cable (5), so as to detect the arrival of the sensor (1) at a given higher level or maximum liquid level.