692,875. Visible signalling apparatus: code-signalling apparatus. GAS ACCUMULATOR CO. (UNITED KINGDOM), Ltd. Sept. 25, 1951 [Oct. 2, 1950], No. 24036/50. Class 118 (ii) [Also in Groups XVIII and XXIV] Means for indicating variations in liquid level comprises a plurality of gas lanterns having individual colour-change means associated therewith, flash-controlling means for regulating the supply of gas to the said lanterns so as to cause the same to flash in regular sequence with an interval between each sequence, and colour control or coder means operated by mechanism responsive to variations in liquid level to select various colour combinations of flash sequence for indicating different levels. Three gas lanterns 1, 2 and 3 are fed from a gas source via a constant pressure device 4 and coupling block 5, the pipes la, 2a and 3a feeding respective pilot burners and the pipes 1b, 2b and 3b feeding the respective main burners through flasher device 7. A manual or automatic valve 8 serves to cut off the operation of the flasher during daytime if so desired. The flasher device 7 is arranged to supply a measured quantity of gas to the burner in each of the three lanterns in turn, to give, for example, one second flashes with an interval of one second between each flash and a longer interval of seven seconds between each cycle of three flashes. A further pipe 6a from coupling block 5 supplies gas pressure to a coder means 6 which controls a spectacletype colour changer 9 associated with each lantern, only that associated with lantern 3 being shown in Fig. 1. Each colour changer 9 comprises three colour screens 9b, 9c, 9d. (Fig. 2) in a holder pivoted on a spindle 10a and having rollers 10c at its lower end on which a weighted member 9g pivoted at 9i presses to normally maintain the colour changer in its mid-position, shown in Fig. 2. Cams 17 on shaft 18 act on valves 12 and 13 to connect pipes 12c and 13c either to the gas pressure in chamber 14 or atmospheric pressure in chamber 14a, and thus the diaphragm chambers 9e and 9f of the colour changer 9 act to move the member 11 linking their two diaphragms into an upward; downward or central position. A slot in member 11 (Fig. 2) engages a lever 10b attached to the spindle 10a to move the colour screens into corresponding positions. The coder means 6 comprises four more valves (not shown) to control the colour changers associated with lanterns 1 and 2. The cams 17 move only in predetermined steps corresponding to discrete changes in liquid level as ascertained by the float 24 and counterweight 25. The pinion 21a on the same shaft as the float mechanism is turned thereby and rotates a wheel 26 loosely carried on cam shaft 18. The wheel 26 has a projecting pin 26a which, in accordance with the direction of rotation, engages one of a pair of spring-loaded levers 27a pivoted on a disc 27 fixed on shaft 18. Each lever 27a is coupled to a pawl 29 engaging a fixed ratchet plate 30, and thus the disc 27 is prevented from moving until the rotation of wheel 26 is sufficient to lift the corresponding pawl 29 and then the cam shaft 18 is turned by disc 27 until the pawl 29 re-engages the ratchet plate 30. The six cams 17 are so profiled that as the shaft 18 is rotated step by step, different colour sequences are exhibited. Where the total variation to be signalled is small, or where larger steps are adequate, only two lanterns may be sufficient, or, conversely, more than three lanterns may be used. Also more than three colour screens may be provided for each lantern. The present embodiment allows 24 useful combinations as sequences in which each lantern flashes the same colour are not utilised to avoid confusion with other navigational signals. If the lanterns and gas supply devices are remote from the cam shaft mechanism, the cams 17 may actuate electric contacts controlling electrically-operated coder means as in Fig. 3 (not shown). The colour change means may be duplicated on the other side of the lanterns to give visual signals in two opposite directions. For an all-round indication, lanterns of an appropriate type may be provided with cylindrical colour screens each consisting of two pivoted semicylindrical parts brought into effective position by diaphragm-operated racks and pinions as in Figs. 4 and 5 (not shown). The liquid level responsive mechanism may effect step-by-step movement of the cam shaft by electrical means and the colourchanging means may be operated electrically instead of by gas pressure.