Abstract: A loud horn for motor vehicles which comprises a hollow housing sealed off by a diaphragm and bearing a vibration electromagnetic generator inside the housing with a coil frame in which the housing is provided with a hole connecting the inside of the housing with the outside allowing for respiration of the loud horn. In order to communicate with said hole, the frame has at least one smaller diameter pipe in order to allow air to penetrate inside the housing, the pipe being provided with a filter preventing water from penetrating inside the loud horn.

Abstract: The invention relates to an acoustic warning device (especially for automobiles) of the type comprising a diaphragm pressed by a spring on a circular lip at one extremity of a horn. According to the invention the said lip is formed on a synthetic material piece socketed on the external periphery of a tubular portion of a foot, the interior of the said tubular portion receiving, by its extremity opposite to the said piece, the said extremity of the horn.

Abstract: An electromagnetic warning instrument has a housing equipped with at least one core carrying an operating electric coil, and a contact-breaker cooperating with a vibrating armature fast with a diaphragm. The coil is mounted on a printed circuit and electrically connected thereto. The printed circuit is mechanically fixed to the housing. The contact-breaker is mounted on the circuit by a mechanical connection which effects an electric connection. The printed circuit carrying the coil or coils can be assembled in advance, preferably by automatic means, then it is fixed on the housing, each coil being simply fitted on to the core. The fixing of the contact-breaker assembly then simultaneously ensures a supplementary mechanical connection for the printed circuit and the electric connection with the contact breaker.

Abstract: An alarm system includes a number of self powered indicating elements each with an integral warning device. Each indicating element includes a control circuit which may comprise a transistor switching circuit, transistor oscillator or part of a wheatstone bridge circuit for example. Each of these control circuits is connected via two lines to a common control element at a position remote from the remainder of the control circuit, such element comprising for example a resistor, a battery or a zener diode dependent on the type of control circuit utilized. A switch is also included to provide, on actuation, either a short circuit or open circuit condition between the two lines. Actuation of this switch or tampering with the lines so as to cause a short circuit or open circuit condition to occur will result in operation of the alarm.

Abstract: Vibrating membrane horn of the type wherein a membrane is applied on a peripheral flange on a case in such a way as to close said case. Said case contains a vibrations generator acting on said membrane and a gasket is interposed between said membrane and said flange. Said gasket consists of an absorbent material impregnated with a water-proofing product.

Abstract: An electro-acoustic signalling horn of the type comprising a case containing an electromagnetic excitation system, a diaphragm subjected to the action of said system, and a sound amplifying box extending a labyrinth chamber. Said box is in a single moulded piece and has a lateral opening opening into said chamber and adapted to receive the diaphragm and the case. Said diaphragm and said case are rendered integral by a metal plate having an edge portion formed over onto a peripheral portion of the diaphragm and the case, the assembly comprising the case, the diaphragm and the plate being maintained in said opening by adhesion of the plate to the adjacent portion of the labyrinth chamber and cooperation of the formed-over peripheral portion of the plate with the edge of the opening.