GB171097A - Improvements in and relating to signalling by high frequency oscillations over line wires - Google Patents

Abstract

171,097. Huth Ges., Dr., E. F., and Schwarz, K. Nov. 2, 1920, [Convention date]. Wired wireless systems; duplex signalling. - Transmitting and receiving coupling wires, by means of which signals are simultaneously transmitted to and received from one or more line wires running adjacent and parallel to the coupling wires, are connected together through inductances or capacities and earthed at a common point in order that, while reception and transmission is not interfered with, damage to the instruments by lightning &c. is prevented. In the arrangement shown in Fig. 1, the transmitting and receiving coupling wires a, b, extending parallel to the conductor l, are connected over inductances s, t to a common point o earthed at e. The coils s, t are directly or indirectly coupled to the receiving and transmitting apparatus, as through the coil r, and the point o may be adjustable along them. Signal currents are cumulative in the coils s, t but static charges &c. pass to earth. Different frequencies are used for transmission and reception. Condensers may replace the inductances s, t and the coupling between the coupling wires and the receiving or transmitting apparatus made capacitative. The coupling wires are tuned by the adjustment of the inductances s, t (or the capacities replacing them) or by varying the frequency of the circuit r to which the wires a, b are coupled. If the two coupling wires a, b extend in opposite directions parallel to the wine l, currents of different phase will be induced in the wire l in the case of transmission, and in the receiving apparatus when receiving. In a modification, two coupling wires a, f, Fig. 6, are coupled by inductances s, t to transmitting and receiving circuits l, m respectively, a third wire n being connected to earth e through the inductances p, q. Transmitted waves pass over the branches a, n, but are prevented from reaching the branch f and the receiving circuit m by a rejector circuit w.. Received waves oppose one another in the inductances s, p, or the coupling between the coils s, p and the transmitting circuit l is made sufficiently loose to prevent received waves from influencing the transmitter. A condenser may be placed across the inductance q to form the rejector circuit. In another modification, the three coupling wires a, n, f are inductively coupled to the separate line wires of a three-phase supply system, the wire between the coils s, t, o being connected to a lightning-protection wire.