1382971 Automatic depth control WHITEHALL ELECTRONICS CORP 4 April 1973 [16 Feb 1973] 16059/73 Heading G3R A flexible, liquid filled marine seismic detector cable has a depth control system including a pressure sensing device in the cable which, according to whether the cable is below or above a predetermined depth, closes an appropriate contact to open an electrically operated inlet or outlet valve respectively allowing liquid to flow into or out of the cable, thus regulating the buoyancy of the cable to maintain it at the predetermined depth. In the embodiment, each section of the cable, which includes hydrophones and is filled with oil, has bellows 27 in contact with the water via aperture 26B and responsive to the water pressure, closing contacts 29A or 29B if the cable moves below or above the predetermined depth. When closed, contacts 29A or 29B energize inlet or outlet valves (32, 33) Figs. 4 to 6 (not shown) allowing pressurized oil, from a supply in the vessel towing the cable, to flow via pipe 23 into or out of cable sections 31 to regulate the cable depth. The bellows, which can be replaced for example by a diaphragm, may be adjustable by signals from the vessel to set the required depth. The control system may be switched off when storing the cable to avoid loss of oil.
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