The large modern trunk exchanges are equipped with relays and lamps for signalling purposes.
High) which contains a fine peal of bells and also serves as a signalling tower.
Among the subjects to which he especially directed his attention were the explosive force of gunpowder, the construction of firearms, and a system of signalling at sea.
It possesses depots for artillery and mines, a meteorological observatory and a signalling station.
At each signalling station was erected an insulated metallic surface facing and near to the ordinary telegraph wires.
Between 1858 and 1868 he was employed in home waters on a variety of special services, chiefly connected with gunnery, signalling and the tactical characteristics and capacities of steam warships.
Lodge, Signalling through Space without Wires, 3rd ed., p. 73, 1899.
Sometimes they occupy the approaches to tablelands, the narrowest points of gorges, or the fords of rivers; sometimes almost inaccessible mountain tops or important points on ridges; and it may be noticed that, where two important nuraghi are not visible from one another, a small one is interpolated, showing that there was a system of signalling from one to another.
Lodge, Signalling across Space without Wires (3rd ed.
If the positive is called the signalling current, the line will be charged positively each time a signal is sent; but as soon as the signal is completed a negative charge is communicated FIG.