Abstract: A circuit for protecting an electronic equipment intended to be connected to at least one first conductor of a communication line, comprising, between this first conductor and a second conductor of the line or the ground to which is connected the equipment to be protected, at least one first branch comprising, in series, a first capacitive element and a first voltage-threshold triggering element, a first resistive element being connected in parallel on the first capacitive element.

Abstract: A high-frequency coupler for extracting a secondary signal representative of a main signal carried by a conductive line, comprising two series-associated, respectively high-pass and low-pass, filters, and the input of which is intended to be connected to said line while its output is intended to provide the secondary signal, the filters being sized so that the sum of their respective attenuations is substantially constant over the coupler passband, and so that their respective cut-off frequencies are in said passband.

Abstract: A series device for protection against a heating of aparallel protection element of an equipment of a telephone line, including a bi-directional cut-off element, of normally on state and placed in series with the parallel protection element, a temperature detection element, and a switching element adapted to turning off the cut-off element when the temperature detected by the detection element exceeds a predetermined threshold.

Abstract: An interface circuit including a galvanic isolation barrier between a transmission line and a user equipment, and a detector for detecting, independently from a transmission, the idle or busy state of the line.

Abstract: An overvoltage protection circuit for a load having a determined resistance value is connected to a supply line with a predetermined polarity. An overvoltage detector is connected across the line. A first switch, normally on, is located in series with a conductor of the line and is controlled (i.e. switched to the off state) by the detector. A second switch, located in series with a resistance having the same determined value R, is disposed between the line conductors and is controlled by the detector in a complementary manner to the first switch.

Abstract: A protection device against overvoltages liable to occur between two supply terminals (A, B) comprises between the terminals, on the one hand, a thyristor (Th) and, on the other hand, first and second zener diodes in series. The anode of the first diode (D1) is connected to the cathode of the thyristor and the cathode of the second diode (D2) is connected to the anode of the thyristor, and a third zener diode (D3) is placed between the thyristor gate and the junction (10) of the first and second diodes. The third diode has an avalanche voltage higher than that of the first diode.