Apparatus for recording, transmission and reproduction of sound or images, cinematographic apparatus and photographic apparatus, Hi Fi stereo amplifiers, crossovers, speakers, video cameras, video reproduction equipment, electric measuring and signalling apparatus and instruments, intruder detection and signalling, sirens, alarms, emergency signalling systems, electronic access control, electronic metal detectors, componants in this class, capacitors, weighing apparatus, electronic scales and componant weighing and counting equipment, nautical and surveying apparatus and instruments, electronic compass, scientific instruments, remote temperature reading, sound and light metering equipment, gas and chemical detectors, optical equipment, fibre optic directional couplers, electro optical devices and systems, magnetic data carrier related equipment, card readers, encoders, data processing and computer based equipment, microprocessor driven devices, fire extinguishing apparatus and automatic home based fire fighting system