POPP-BRANLEY NON-STN TONIC SYSTEM. In a system devised by Professor Eduard Branley, the original inventor of the coherer, and 31. Victor Popp of France, the general arrangement shown in Fig. 20 is employed. The chief feature of this system lies in a type of coherer in vented by Branley. This consists of a bronze disk.Fig.
20, with three steel legs fixed on its surface form ing a tripod at right angles to its plane. The legs are brought to a point and polished, after which they are oxi dized by heating in an alcohol flame and tempered; this gives them a thin insulating film of oxide, which pre vents a low-voltage current from flow ingthrough the con tact. but when a high-frequency oscillation surges through it the film is broken down, the direct current then follows aril indicates the signal.
It is a eoherer of exceptional sensitiveness and stability. On Plate II. is shown the coherer mounted on the Morse register, which also steps up an alternating current generated by the dynamo 1 from 500 to 25,000 volts, which charges the Leyden jars, 7. 8, to their capacity, when they discharge through the air-gap. G. set ting up oscillations in the aerial wire, 4, and the earthed wire, 5. The transmitting apparatus is shown on the Plate.
The receiver (see diagram Fig. 22) consists of a new type of wave detector, 1', 1", a battery, 4', a telephone receiver, 6'; the receiver is connect ed in shunt with the coherer through the con denser, 5'. Resistances, 2' 2" and 3', are in serted to compensate for the excess of battery current. The wave de tector operates diamet rically opposite to that of the eoheren; in that its resistance is in creased by the cumula tive action of the oscillations instead of decreased. For this reason it is termed an anti-eoherer ; in stead of metallic filings placed between the eon ductor plugs of the coiterer tube, an oxide of lead mixed with glycerin is employed. It is shown on the accompanying Plate. The action is electro lytic in character. simile the direct current from the battery builds up connecting threads and these are disrupted when the oscillations take place. Systems have been devised by Monsieur E. Ducretet of France. Seilor Cervera Baveria of Spain, Monsieur E. G. Foresio of Bel gium, and others, but these are merely modi fications of the first system operated in 1896 by Guglielmo Marconi. '