Abstract: A method for underwater, acoustic transmission, characterized in that at the transmitting side, the signal to be transmitted first is sampled, digitized and stored and then un-sampled and un-digitized at a frequency less than the sampling frequency and is thus transmitted in analogue form, and in that at the receiving side the signal is correspondingly sampled, digitized and stored at the said un-sampling and un-digitizing frequency and then is re-read at the said sampling frequency.

Abstract: A device for measuring the level of a variable signal delivered by a sensor. It comprises a series of attenuators, receiving the signal from the sensor, a squaring and integrating chain for converting the value of the signal delivered by the attenuators into its root-mean-square value, and a recorder. The attenuations are calibrated in dB. The device comprises an AGC circuit, receiving the output signal from the squaring and integrating chain, for switching the attenuators and controlling the recorder. The output signal from the attenuators is maintained constant.