Four-wire terminating circuit

摘要

A four-wire termination circuit has a series arrangement of a current source controlled by a transmitting arm of a four-wire line and a first resistor. This arrangement is connected in parallel to a two-wire line terminal impedance formed by a second resistor and an impedance. The terminal impedance terminates the two-wire line in reflection-free fashion. Voltages dependent upon a transmitted signal current which are equal in value but opposed in phase appear across the first and second resistors. A voltage which is dependent upon a received signal current from the two-wire line appears across the second resistor. In a receiving arm of the four-wire line, an intermediate value voltage is present which is independent of the transmitted signal in the transmitting arm.