Patent GB-190704593-A (GB)
Title: Improvements in Transmitting Apparatus for Wireless Telegraphy.
Filed: 1907-02-25
Granted: 1908-02-20
Abstract: 4593. Marconi, G., and Marconi's Wireless Telegraph Co. Feb. 25. Telegraphs.-In order to obtain, without the use of a spark - gap, a frequency sufficiently high, together with a current of sufficient intensity for wireless telegraphy, a specially-constructed reversing-commutator is used, in connexion with ordinary direct or alternating current. Two metal disks a, b, Figs. 3 and 4, of the same size, and insulated from, but rigidly attached to each other and mounted on co-axial shafts, have equal numbers of equidistant teeth a<1>, b<1> cut in their circumferences ; the disks are so arranged that the teeth of one are spaced midway between the teeth of the other, as shown in Fig. 4. The two disks are electrically connected to the opposite poles of a dynamo so that every alternate tooth of the commutator is in connexion with one pole of the source of current, while the other teeth are connected to the other pole. A collector disk e, Fig. 1, the rim of which is equal in breadth to the total breadth of the commutator rim, is constructed similarly to each of the disks of the commutator b, and the distance between its teeth is the same as that between the teeth of either of the disks of the commutator. The collector is rotated on a parallel shaft, in close proximity to, but not in absolute contact with the rotating commutator, and the voltage of the dynamo must be sufficiently high to cause a spark to leap across the small air gap separating the two wheels. The direction of rotation of the two disks being the same, the collector disk is put alternately in contact with the opposite poles of the dynamo. The brushes g, h lead the current to the commutator, and the brush j carries the current from the collector. In place of the above arrangement, the commutator disk may be stationary, while the collector takes the form of a bar which is rotated in such a manner as successively to pass in close proximity to the oppositely charged contacts of the commutator. Or the commutator disk may be omitted and the collector wheel rotated close to two or more fixed contacts spaced and connected as described for the teeth of a commutator wheel ; or the generator wheel alone may be employed if rotated close to one or more fixed contacts. A higher voltage may be used if the wheels are rotated in compressed air, or if a jet of compressed air is caused to impinge on the place where contact is made. By arranging the teeth on the commutator in groups, the transmitting - apparatus may be arranged to transmit, instead of a continuous stream, regular groups of oscillations, to which the receiving-apparatus may be tuned to respond. The collector is connected through an inductance n to one plate of a condenser k, the other plate of which is connected to the middle point of a pair of condensers l placed as a shunt across the terminals of the dynamo. The condensers l may be omitted, in which case the condenser k is connected to a point in the winding of the generator of the source of electricity where the difference of potential between the said point and one of the poles is half that existing between the poles. If the condenser l is present, the condenser k may be omitted. The secondary m of a jigger having a primary coil n is in series with the antenna o.