| 摘要 |
Simultaneous outgoing and incoming transmission of information via a 2-wire line is possible only at great cost. In the case of long-distance connections, feedback circuits should also be avoided, which in particular is possible in 4-wire mode only. These disadvantages are avoided in the invention by coding the information in both directions using the amplitudes of the half-waves or cycles in each case of an alternating current of the same frequency, the two alternating currents being phase-shifted through 90 degrees in relation to each other. In the case of common electric circuits, the two alternating currents are then added together in the manner of quadrature amplitude modulation so that the information is retained.
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