Remote control apparatus; data processing apparatus; igniting apparatus, electric, for igniting at a distance; gauges; measuring apparatus; measuring devices, electric; measures; flowmeters; gas testing instruments; gasometers [measuring instruments]; hygrometers; hydrometers; detectors; smoke detectors; telerupters; dosage dispensers; electric installations for the remote control of industrial operations; electro-dynamic apparatus for the remote control of signals; acoustic alarms; couplers ...