Abstract: A method of determining, by a first device capable of transmitting a two-state signal over a single-wire connection to a second device, the binary state of data transmitted by the second device over said connection, the state being determined according to the slope of a rising edge of the two-state signal.

Abstract: A method of detection of the presence of a contactless communication element by a terminal emitting an electromagnetic field, in which an oscillating circuit of the terminal is excited at a frequency which is made variable between two values surrounding a nominal tuning frequency of the oscillating circuit; a signal representative of the load of the oscillating circuit being interpreted to detect that a reference voltage has not been exceeded, which indicates the presence of an element in the field. A presence-detection circuit and a corresponding terminal.

Abstract: A method of detection of the presence of a contactless communication element by a terminal emitting an electromagnetic field, in which an oscillating circuit of the terminal is excited at a frequency which is made variable between two values surrounding a nominal tuning frequency of the oscillating circuit; a signal representative of the load of the oscillating circuit being interpreted to detect that a reference voltage has not been exceeded, which indicates the presence of an element in the field. A presence-detection circuit and a corresponding terminal.

Abstract: An electromagnetic transponder comprising: an oscillating circuit; a first rectifying bridge having its A.C. input terminals connected across the oscillating circuit and having its rectified output terminals connected at least to a voltage regulator in charge of providing a supply voltage; and a second rectifying bridge, of dimension smaller than that of the first bridge, having its two A.C. input terminals connected across the oscillating circuit and having at least one output terminal connected to a demodulator of data sensed by the oscillating circuit.

Abstract: A dual-mode smart card comprising several pads of physical contact with an external reader and two pads of connection to an antenna for a contactless operation, and comprising a voltage regulator capable of extracting from a radio frequency excitation reaching the antenna, a supply voltage of the chip's processing circuits, this regulator being controllable by a central circuit to be deactivated in the presence of a supply voltage on contacts of the chip.

Abstract: An amplitude demodulator comprising a capacitive element for filtering a first D.C. component of a received signal, an element for detecting edges in the signal provided by the capacitive element, and at least one switching element for forcing, at least after detection of an edge, the returning of the signal provided by the capacitive element to a second D.C. component.

Abstract: An electromagnetic transponder intended to draw the power necessary to its operation of from a field radiated by a terminal of transmission of a carrier at a first supply frequency and to back-modulate the received signal at the rate of a sub-carrier at a second frequency lower than the first one, and comprising means capable of demodulating and decoding signals modulated by said sub-carrier, as well as a system of communication between such transponders.