Abstract: An electromagnetic detector designed to monitor road traffic, responsive to a modification of an electromagnetic field produced by the presence of a metallic mass in the vicinity thereof, comprises a metal base on which are disposed a transmitting coil creating a field and a receiving coil whose axis deviates from the perpendicular to the base. The receiving coil detects a measuring field created by the currents induced in the base by the transmitted field. The processed signal is the resultant of the signal produced by the presence of a metallic mass in the transmitted field and by the signal due to the measuring field.

Abstract: An electromagnetic detector sensitive to the intrusion of a metallic mass (e.g., a road vehicle) into its field of radiated energy comprises, disposed on a metallic support, a transmitter coil and two strongly coupled receiver coils. These receiver coils are located at a distance from the transmitter coil and on opposite sides of the axis thereof. The axis of the transmitter coil and the common axis of the receiver coils are roughly perpendicular to each other. The presence of a metallic mass in the field around the detector induces signals in the receiver coils varying in relative phase according to the extent of the modification of the generated electromagnetic field. The output voltages of the receiver coils are combined to form a resultant square wave comparison with a reference square wave produces an output signal depending on the phase difference thereof.

Abstract: A radio receiver, especially one installed in a road vehicle, has a first section for picking up special message signals such as road-traffic information and a second section for picking up a normal radio program. A relay energizable by the special signals, normally connected to the first receiver section, automatically switches a loudspeaker from the second receiver section to the first one whenever such signals begin to arrive. A circuit breaker in series with the relay can be manually controlled by a pushbutton, through the intermediary of a bistable storage circuit, to deactivate the relay for shifting back to audible reproduction of the normal program at the will of the user even while the special message signals continue to arrive; another actuation of the pushbutton in the presence of these signals restores the original condition.

Abstract: A distress-signal generator aboard a vehicle includes a transmitter with a self-locking relay for energizing a high-frequency oscillator from a local battery in response to one or more trigger signals from respective detectors, specifically an impact detector and a deformation detector. The impact detector comprises two coacting members, one of them fixed to the vehicle body and the other freely movable with reference thereto, the elastically suspended mobile member being generally spool-shaped and having its waist received in an oblong opening of the plate-shaped fixed member. With the major axis of the oblong extending in the direction of vehicle motion, contact between the two members occurs in response to relatively small transverse and vertical accelerations but only with relatively large longitudinal acceleration; relative torsion is detected by a horizontal pin on the mobile member bracketed by two stops on the fixed member normally spaced therefrom.

Abstract: A traffic-surveillance system comprises a radar equipment coupled to a transmitter/receiver antenna. This antenna is formed by a transmission line including an elongate hollow conductor with leakage losses, such as a slotted coaxial cable or waveguide, producing along its length an electric radiating field. Any metallic mass, such as a vehicle, located within that field reflects part of the radiated energy which is then picked up by the line. Part of the reflected energy is absorbed in the characteristic impedance of the line while the remainder is conveyed to the radar equipment where it is processed to yield the required information concerning the vehicle.