inside the string in a variant of the acquisition system a high frequency of measurement transmission is obtained by electric links consisting of cable 5 line 16 and 17 and surface cable 14 certain downhole sensors which require no high frequency sampling can transmit their measurements through other channels by pressure wave or electromagnetic wave for example sub 4 can include the necessary electronics to compact the information provided by at least one drilling signal the characteristic coefficients of signal segments can then be transmitted either through the electric conductor of the device of fig1 or by pressure wave or electromagnetic wave or by any other suitable transmission means sub 4 can also comprise the electronic means of automatic segmentation into homogeneous segments and means for selecting the characteristic segments of a behaviour of the determined drilling a behaviour which will be brought to the operator 39 s attention after transmission of the characteristic coefficients to the surface fig1 b shows a conventional drill rig in which one has inserted in the drill collars a measuring sub 4 which records at least one drilling signal an electronic installation 20 including the signal compaction means an installation 21 for coding and transmitting to the surface the characteristic coefficients of the signal transmission can be achieved by pressure waves in the column of fluid inside the drill string a pressure detector 22 located on the surface injection line 23 transmits the pressure waves to a surface processing installation which decodes the pressure waves to obtain the characteristic coefficients the surface installation can identify the behaviour according to a data base or to particular instructions or reconstruct the signal in order to give the operator for example analog measurements fig2 shows an example.