Abstract: The present invention relates to an alarm device for doors in vehicles which is located in a hollow rubber tube and gives alarm as the tube is compressed. The device can be adjusted to be sensitive by placing in one end of the tube a light transmitter and in the other end a light receiver producing a signal which changes according to the light intensity received by the receiver and by compensating slowly occurring changes in said light intensity so that the light intensity of the light transmitter in a corresponding manner is corrected.

Abstract: The invention relates to a device for regulating the power in electrical apparatuses, especially fluorescent lighting fittings. To each apparatus (6) is connected an inverter (1-5, 7-11; 12; 13) in which the control circuit of the oscillator transistor (1) is provided with an adjustable RC circuit (8, 9).The power of a plurality of apparatuses included in the same group can be adjusted through one pair of conductors by connecting in parallel with the RC circuit (8, 9), on one hand, the contacts of a relay (10) and, on the other hand, an opto-insulator (11) whereby the relay (10) is connected to one conductor of the pair of conductors and the opto-insulator (11) to the other conductor.

Abstract: A means for regulating the power of a fluorescent tube in a vehicle supplied by a DC source by providing the control circuit of an oscillator transistor of an inverter with an adjustable RC circuit. Even very much dimmed tubes can be lighted with the use of a switch by-passing the RC circuit.