Patent GB-248823-A (GB)
Title: Improvements in submarine cable and like telegraph systems
IPC: H04L5/14
Filed: 1924-12-06
Abstract: 248,823. Western Electric Co., Ltd., (Western Electric Co., Inc.). Dec. 6, 1924. Restoring or modifying imperfect signals; balancing networks; eliminating effects of disturbing currents.-The apparatus at the receiving station in connection with an inductivelyloaded cable is of an impedance which is substantially higher for frequency components below than for frequency components above the signalling frequency. The end of the single core 5, Fig. 1, of the cable is spliced to one core 7 of a twin-core terminal section 6, and a switch 8 connects the core 7 either to the local transmitter T or to the receiving apparatus R. The other twin core 9 is connected at the shore to the apparatus R and at the sea end is grounded on the armouring of the cable through a resistance 10 to constitute a balancing return circuit for preventing disturbances due to local fields. The value of the resistance 10 approximates to the characteristic impedance of the single-core section 5. All the cores may be loaded with the nickel-iron alloy described in Specification 188,688, [Class 82 (i), Metals, Extracting &c.]. The receiver, e.g. a siphon recorder, is connected to the cable through a valve amplifier A, a shielded transformer 26 preferably constructed as described in Specifleation 248,822, and a network N adjusted to have the appropriate impedance characteristics. The receiver 29 may be located, for convenience at the end of a cable 30 connecting it to the amplifier, a local monitoring receiver 31 being also provided. The network N comprises in series with the transformer primary a condenser 21 shunted by a resistance 23, and in shunt with the transformer primary an inductance 22 with a shunt resistance 24 and a series resistance 25, and each of the elements of the network is adjustable. Fig. 2 shows an amplifier comprising four valves with shaping networks between the valves. The plate circuit of the valve 2A1 is coupled to the shaping network 101 by a high resistance 102 and a condenser 103. The network 101 is designed to amplify only the higher frequencies and comprises condensers 104, 107, resistance 105, and auto-transformer 106 with an abnormally high primary resistance, each element being adjustable. The battery 108 for bias. ing the grid of valve 2A2 is connected as shown betwen the elements 106 and 107. The shaping network 109 betwen the valves 2A2 and 2A3 comprises inductance 112 shunted by resistance 114 and in series with condenser 113 shunted by a grid leak resistance 115, the elements 112, 113. and 114 being adjustable. A similar network 120 is arranged between the valves 2A3 and 2A4. Fig. 3 shows a modification of the amplifier of Fig. 2 with a wider rauge of adjustment of the shaping elements. The coupling resistances 102, 110, and 117, and the condenser 103 are made adjustable, and the grid biasing batteries 100, 108, 116 and 125 are connected adjacent to the grounded sides of the filaments. The network 109 is modified and comprises a potentiometer 130, resistance 114, condenser 113, and inductance 112 arranged as shown. The network 120 is also modified and comprises resistance 131, 122, condenser 123, and inductance 121 arranged as shown.