Telephone signalling system between two points - uses set of grouped signal wires and has single return through earth wire

摘要

The points are already connected by wires, and an earth wire is used. The wires are combined in a group and they are kept separate from the earth wire (17). Signals in the form of speech frequency or of h.f. modulated signals are applied by a transmitter station (3) to the wires as a group. They travel in the same direction to a receiving station, and return through the earthed wire (17). The earthed wire is connected to several capacitors (13, 14, 15, 16).