To prevent being able to capture sensitive signals between electronic circuits placed on an electronic card, these circuits are arranged in a protected zone in such a manner so as not be distant from each other by more than a determined distance. The circuits of the protected zone comprise at least one control circuit. The electronic card further comprises another zone defining a non-protected environment; the circuits of this zone do not need to comply with the distance constraint. The communication between the circuits of the protected zone and the non-protected environment is carried out by means of a communication circuit allowing or not allowing the electrical signals to pass. The passage of the electrical signals in the communication circuit is conditioned by an electrical control signal sent by the control circuit. The invention also relates to a method allowing the control circuit to be blocked if the electrical status of the signal controlling the passage of the signals does not correspond to the status imposed by the control circuit.