Abstract: A direct and continuous receiving and measuring device for electrical, magnetic and acoustic signals comprises an amplifier stage and a broadband filtering stage at the input, a local oscillator for supplying a reference signal, a measuring stage, a mixer to which the local oscillator and the broadband filtering stage are connected and a low frequency filtering stage connected to the mixer.The invention also includes the process of carrying out the measurement.

Abstract: A recording apparatus for recording digital signals corresponding to components of telluric and magnetic fields. The apparatus comprises an analog input stage, a low pass filter stage, an analog output stage, an analog multiplexer and an analog-to-digital converter and recording system for recording the digital signals. A gain computing module is provided as well as a recording selector to achieve variable amplification gains in the analog input and output stages as well as variable frequency bands in the low pass filtering stage to accommodate different frequency input signals for low frequency recording, intermediate frequency recording and high frequency recording.