BRAUN'S RESONANCE SYSTEM. Another sys tem employing resonance to effect syntonization is clue to Professor Ferdinand Braun of Ger many. The oscillator and resonator consist of distinct open and closed circuits, as shown in the diagram Fig. 17. In the oscillator, A, the high frequency currents surge through the closed cir cuit formed by the spark-gap, s, the con densers. C, C, and the primary of the trans former coil, L, where they are impressed upon the secondary of the transformer, M, in the open circuit oscillator; this oscillator radiates waves as rapidly as the energy is supplied to it, yet of a definite wave length; the aerial wire, a, should be one-fourth of the wave length ; the opposite terminal, b, is. not grounded, but to maintain the relations be tween the coefficients the wire b is made equal to a.
The receiver, B, comprises the aerial wire, a', and its complementary wire, V, separated by the condensers, C, C. This is a compound-circuit res onator. The closed-circuit resonator is joined through c, c and the primary of a transformer, L; oscillations set up by the waves in this circuit are transformed into an open-circuit resonator through the secondary coil by the transformer,. N; its terminals connect with two wires. (1, e, each of which is one-fourth of the wave length, and equal in length to the aerial wire; the coherer is included in the circuit of the wire e, where the amplitude of the wave is greatest. An ordinary eoherer of steel filings is employed in a tube which is not exhausted of its air; the tapper is operated by clockwork actuated by the relay and the message is received by a Norse printing register.
FESsENDEN TUNED SYSTEM. This system of syntonic wireless telegraphy is the invention of Professor R. A. Fessenden, and embodies many original features. The diagram Fig. 18 illus trates a combined sending and receiving sys tem. The transmitter comprises the aerial wire, 1, the induction coil, 2, spark-gap, 3, and a key, 4, for throwing the aerial wire in and out of tune; the tuning of the oscillator and resonator is accomplished by a variable inductance and capacity made of a number of parallel wires or grid immersed in oil and controlled by movable contacts, 5; this eliminates condensers and coils for obtaining given values of capacity and inductance, and preserves the proper relations between these co efficients. The resonator of the receiver com prises a similar grid. 9, used for tuning an electric wave detector, actuating the tele phone receiver; the lio•sr code is employed, the messages being read from the clicks in the telephone receiver. The wave detector is novel in the art of wireless telegraphy; it con sists of a short loop of silver wire. 13, Fig. 19, having a platinum core; this wire is drawn down to .00v2. inch ; the loop is then fastened to the leading•iu wires, 14; the tip of the silver loop is then dissolved away with nitric acid, leaving the platinum core exposed ; the whole is then sealed in a glass bulb, 15, which is finally exhausted.
acts as a tapper for restoring the eoherer to its high resistance.