System for supplying compressed gas to several gas-fed devices, comprising: - a gas intake for connection to a gas source; - an end gas outlet for connection to a first gas-fed device; - a liquid piston gas multistage compressor which comprises at least two compressor stages connected serially in an ordered chain between the gas intake and the end gas outlet, each compressor stage comprising at least one cylinder supplied with driving liquid, and also comprising a liquid high-pressure supply device arranged for alternately increasing and decreasing a driving liquid quantity contained within the cylinder, so as to load, compress and discharge gas at the compressor stage, each compressor stage other than the first one in the chain, and called higher compressor stage, being connected to process gas which is outputted by a preceding compressor stage situated in the chain just before said higher compressor stage, through an intermediate gas duct connecting said preceding compressor stage to said higher compressor stage, so that gas flowing from the gas intake is pressure-increased each time it is processed by one of the compressor stages, and gas outputted at the end gas outlet has been processed successively by all the compressor stages of the chain; characterized in that it further comprises: - an intermediate gas outlet arranged in one of the intermediate gas ducts connecting two compressor stages (2, 3) which are successive in the chain, said intermediate gas outlet being intended for connection to a second gas-fed device through an adjustable draw-off valve; and - a first pressure sensor arranged for sensing gas pressure at the gas intake, a second pressure sensor arranged for sensing gas pressure at the intermediate gas outlet upstream the draw-off valve with respect to gas flow direction in said intermediate gas outlet, and a third pressure sensor arranged for sensing gas pressure at the end gas outlet; and in that the liquid high-pressure supply device of a first compressor stage of the chain comprises first regulation means arranged for varying a gas capacity of said first compressor stage based on first measurement results issued by the first pressure sensor, the system further comprises second regulation means arranged for adjusting the draw-off valve based on second measurement results issued by the second pressure sensor, and the liquid high-pressure supply system of a last compressor stage in the chain comprises third regulation means arranged for varying another gas capacity of said last compressor stage based on third measurement results issued by the third pressure sensor. - a gas intake for connection to a gas source; - an end gas outlet for connection to a first gas-fed device; - a liquid piston gas multistage compressor which comprises at least two compressor stages connected serially in an ordered chain between the gas intake and the end gas outlet, each compressor stage comprising at least one cylinder supplied with driving liquid, and also comprising a liquid high-pressure supply device arranged for alternately increasing and decreasing a driving liquid quantity contained within the cylinder, so as to load, compress and discharge gas at the compressor stage, each compressor stage other than the first one in the chain, and called higher compressor stage, being connected to process gas which is outputted by a preceding compressor stage situated in the chain just before said higher compressor stage, through an intermediate gas duct connecting said preceding compressor stage to said higher compressor stage, so that gas flowing from the gas intake is pressure-increased each time it is processed by one of the compressor stages, and gas outputted at the end gas outlet has been processed successively by all the compressor stages of the chain; - an intermediate gas outlet arranged in one of the intermediate gas ducts connecting two compressor stages (2, 3) which are successive in the chain, said intermediate gas outlet being intended for connection to a second gas-fed device through an adjustable draw-off valve; and - a first pressure sensor arranged for sensing gas pressure at the gas intake, a second pressure sensor arranged for sensing gas pressure at the intermediate gas outlet upstream the draw-off valve with respect to gas flow direction in said intermediate gas outlet, and a third pressure sensor arranged for sensing gas pressure at the end gas outlet;