 Modern submarines use either swim-out systems or a pulse of water to discharge the torpedo from the tube, both of which have the advantage of being significantly quieter than previous systems, helping avoid detection of the firing from passive sonar.Earlier designs used a pulse of compressed air or a hydraulic ram.Early submarines, when they carried torpedoes, were fitted with a variety of torpedo launching mechanisms in a range of locations; on the deck, in the bow or stern, amidships, with some launch mechanisms permitting the torpedo to be aimed over a wide arc.