_Speaking Tube._--The rubber speaking tube which was the forerunner of the telephonic apparatus is now practically obsolete, though it is still used in isolated cases.
_Submarine Electric Lamps._--Various forms of submarine lamps are used, from a powerful arc light to a self-contained hand lamp, the former giving about 2000 or 3000 candle-power, and requiring a steam-driven dynamo to supply the necessary current, the latter (fig. 5) giving a light of about 10 candle-power and having its own batteries, so that the diver carries both the light and its source in his hand. These submarine lamps are all constructed on the same principle, having the incandescent lamps, or carbons as the case may be, enclosed in a strong glass globe, the mechanism and connexions being fitted in a metal case above the globe, which is flanged and secured watertightly to the case.
_Self-contained Diving Dress._--The object of the self-contained diving dress is to make the diver independent of air supply from the surface. The dress, helmet, boots and weights are of the ordinary pattern already described, but instead of obtaining his air supply by means of pumps and pipes, the diver is equipped with a knapsack consisting of a steel cylinder containing oxygen compressed to a pressure of 120 atmospheres (= about 1800 lb.) to the square inch, and chambers containing caustic soda or caustic potash. The helmet is connected to the chambers by tubes, and the oxygen cylinder is similarly connected to the chambers. The breath exhaled by the diver passes through a valve into the caustic soda, which absorbs the carbonic acid, and it is then again inhaled through another valve. This process of regeneration goes on automatically, the requisite amount of oxygen being restored to the breathed air in its passage through the chambers. This type of apparatus has been used for shallow water work, but the great majority of divers prefer the apparatus using pumps as the source of the air supply.
An emergency dress, using this self-contained system for breathing, has been designed by Messrs Fleuss and Davis, of the firm of Siebe, Gorman & Co., primarily as a life-saving apparatus, for enabling men to escape from disabled submarine boats.