The limitation of the gain of two-way telephone repeaters by impedance irregularities

BECAUSE of the fact that it is a difficult and expensive matter to build and maintain the high grade circuits that are required for modern long distance telephone transmission with repeaters. many workers in this field have attempted to devise some form of two-way repeater which would be able to give as large a gain as desired without singing or poor quality due to irregularities existing in the lines. They have thought that if such a repeater could lie constructed it would permit the use of lines less carefully built and, therefore, cheaper than are at present required, and that fewer repeaters would lie required because larger gains could be obtained at each repeater.