Abstract: The invention relates to a method of measuring the height of a liquid using a high-frequency line probe. According to the invention, a comparison is made, on an electric circuit (3) which is supplied with high-frequency alternating current, between the impedance of a coaxial or non-coaxial line probe (1) and a reference resistor (17), using a resistive measuring bridge (7). The probe (1), which is submerged in a lank of the fluid of which the height is to be determined, forms one measuring arm of the measuring bridge and the above-mentioned reference resistor (17) forms an opposite arm of the measuring bridge, the comparison signal resulting from the alternative measurement of the signals on each of said arms using a suitable detector. Subsequently, the comparison signal is processed in order to obtain the calculation of the height of the liquid according to the permittivity thereof, the length of the probe (1) and the circuit (3) power line frequency.

Abstract: The invention relates to a method of measuring the height of a liquid using a high-frequency line probe. According to the invention, a comparison is made, on an electric circuit (3) which is supplied with high-frequency alternating current, between the impedance of a coaxial or non-coaxial line probe (1) and a reference resistor (17), using a resistive measuring bridge (7). The probe (1), which is submerged in a lank of the fluid of which the height is to be determined, forms one measuring arm of the measuring bridge and the above-mentioned reference resistor (17) forms an opposite arm of the measuring bridge, the comparison signal resulting from the alternative measurement of the signals on each of said arms using a suitable detector. Subsequently, the comparison signal is processed in order to obtain the calculation of the height of the liquid according to the permittivity thereof, the length of the probe (1) and the circuit (3) power line frequency.

Abstract: A system comprises a central unit and a plurality of display modules each adapted to show on a display information received from the central unit, for example for displaying prices in a store. The central unit comprises a transmitter including a current loop fed with a low-frequency signal modulated according to the information to be transmitted and the system comprises, associated with each display module or group of display modules, a receive circuit, a receive antenna coupled electromagnetically to said current loop and a device for activating the receive circuit at predetermined periods for a limited duration. Each transmission of information by the central unit is preceded by the transmission of a reactivation signal which, when detected by the receive circuit during a phase in which the latter is active, causes it to be held in the active state for at least part of the duration for which said information is transmitted.