Four wire telephone connection of remote extension to PBX - has two stable conditions for speech amplification on line with repeaters and transmitters

摘要

The four-wire telephone line links an extension of a remote station to a private branch exchange. The line contains repeaters. Both ends of the line are forked (6, 7) with an equaliser (8, 9). The speech amplification on the four-wire line has two stable conditions. The reaction time does not exceed a few milliseconds. One of the repeaters (13) is in the transmission pair and the other repeater (14) is in the receiving pair.