Patent GB-100453-A (GB)
Title: Means for Telephonic Communication to and from Moving Railway Trains and the like.
Inventor: WERNER VICTOR GABRIEL
IPC: H04B3/60
Filed: 1916-05-09
Abstract: 100,453. Werner, V. G., and Warfvinge, K. H. May 11, 1915, [Convention date]. Telephone systems; induction, preventing.- Relates to inductive systems of telephony for communicating between a fixed station and a moving train or other vehicle, and comprises means for minimizing the inductive effects on adjacent lines of the currents in the stationary circuit, and for eliminating disturbances caused by earth currents. In the arrangement shown in Fig. 1, the stationary circuit comprises an aerial wire A, B earthed at each end, the middle point C being also earthed through a two-way switch at the fixed station, which may put either the battery 3 and microphone 2, or the receiver 4, in connexion with the line. The moving circuit E, which is preferably mounted on the roof of a carriage, has a similar two-way switch 6 for connecting the microphone 7 or the receiver 9. The currents in the branches AC, CB of the aerial are oppositely directed and thus do not influence long adjacent conductors. As shown in Fig. 2, portions of the existing telegraph lines T may be used in the stationary circuit, which is completed by a wire 10, 11, 12 on the opposite side of the track. The fixed station D is bridged across the rectangle, and the resistances of the branches are adjusted by a variable coil 13 so that telegraphic currents in the wire T do not affect the fixed station D. When a telegraph station is situated at the point C of the line T, it is shunted by a wire with two condensers in series, and the fixed station D is connected between the condensers. In the arrangement shown in Fig. 5, each end A, B of the utilized portion of the line T is earthed through a condenser 16, 17, and a condenser 22 is also placed in series with the fixed station D. Choking-coils 18, 19 are inserted in the line T beyond the points A, B and their outer ends are earthed through condensers 20, 21. A variable resistance 23 is provided in one branch of the circuit. When a two-wire telephone line forms the stationary circuit, choking-coils 24, 25, 26, Fig. 6, are connected across the wires at the points A, B, C, and their middle points are earthed. The local talking-circuit thus passes through the halves of the choking-coils in opposite directions, and their inductance is neutralized, whereas the inductance of the coils as a whole prevents them from short-circuiting the wires for ordinary telephone traffic. A variable resistance may be inserted in the earth connexion of one of the coils, or resistances may be placed in each wire of the line CB. In this case, the resistances may be short-circuited when the receiver at the station D is hung up. These resistances may comprise coils wound on a single iron core in such manner that the inductance is neutralized by currents representing the through-traffic on the line. Any number of choking-coils such as 24, Fig. 6, may be arranged at regular intervals along the line, and each may have a station D in its earth connexion, the stations being short-circuited through a switch which is opened when the receiver is taken up. In the arrangement shown in Fig. 11, the station D is normally disconnected from the choking-coil 36, and a transformer primary 37 is inserted in its place, the secondary 38 being connected across the telephone wires or to a separate circuit including a station D<1>, which may be at some distance from the passing train.