GB202284A - Improvements in electrical networks - Google Patents

Abstract

202,284. Western Electric Co., Ltd., (Assignees of Zobel, O. J.). Aug. 9, 1922, [Convention date]. Artificial lines.-In telephone &c. net-works of the general types shown In Figs. 1 and 5, having impedance elements Z1, Z2, the characteristic impedance of the network is made equal to a constant resistance R for all frequencies by the use of series and shunt impedances Z11, Z21 connected by the relation Z11, Z21 = R<2>, as shown for example in Fig. 7. The network may be terminated at any mid-series point, such as 25<1>, 26', by a resistance R without affecting this characteristic impedance. The propagation constant of such networks is found to be a function of Z11/R, and a graphical method of obtaining the attenuation and phase components for the network of Fig. 7 is given. Fig. 15 shows the application of the invention to insert in a reactanceless circuit an instrument T with impedance without the introduction of reactance by using it as an element in a network section, an equivalent impedance Z11 and resistance R' being found by trial, and the impedance Z21 being calculated from the terminal resistance R. A network section may be inserted as an attenuation equalizer in a line whose attenuation curve is known, a suitable impedance Z11 being found by trial from the curve and the calculated equation for the propagation constant.