Abstract: In order to convert an analog signal of digital data transmission into a digital signal, the device embodying the invention comprises a passive analog circuit comprising a capacitor charged by the analog signal via a first resistor, the voltage at the terminals of the capacitor being applied via a second resistor, at the input of a digital circuit comprising a threshold comparator applying, to a flip-flop, a logic signal which is a function of the result of the comparison with a threshold of the voltage at the input, a means for periodically applying at the input a charge or discharge pulse so as to bring the voltage at the input back to the threshold voltage, a counting circuit for periodically determining a number representative of the analog signal, obtained from subtracting the number of discharges from the number of charges.