United States Patent 4,004,109
January 18, 1977

Hybrid Circuit
Frank S. Boxall

Filed May 9, 1975
Image of US PATENT 4,004,109

Abstract of the Disclosure

A direct coupled transformerless hybrid for providing signal conversion between a balanced bidirectional transmission path and a pair of unbalanced unidirectional transmission paths, for providing direct current to the bidirectional transmission path, for suppressing longitudinal mode signals supplied by the bidirectional transmission path, and for providing signal balance to suppress transmission of reflected echoes from the invoming unidirectional transmission path to the outgoing unidirectional transmission path.
Of the several embodiments disclosed each includes a plurality of current mirror circuits, some of which include elements of complementary conductivity type to the elements of the remaining current mirror circuits. Each current mirror circuit has a coltage supply terminal, an input terminal, at least one output terminal, and means for supplying a current to the output terminal proportional to the current at the input terminal.
Means are further provided for automatically adjusting signal balance at the unidirectional transmission path side of the hybrid in accordance with the resistance, and thus the length of, the bidirectional transmission path.
Figure descriptions: cover graphic

  • a block diagram of a first embodiment of the invention adapted for use with a subscriber loop.

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2,5111,948 06/1950 Wang 3,180,947 04/1965 Haselton, Jr. et al 3,530,260 09/1970 Gaunt, Jr. 3,700,831 10/1972 Aagaard et al
National Museum of American History
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