Patent ID: 8564302

Claim:
A test instrument for testing of a line under test having a first conductor and a second conductor comprising: a coupling transformer having a line under test side and a test instrument side; a positive side DC isolation circuit providing an electrical connection between said line under test side of said coupling transformer and the first conductor of the line under test said positive side isolation circuit configured to provide transmission of broad band signals; a negative side DC isolation circuit providing an electrical connection between the line under test side of said coupling transformer and second conductor of the line under test said negative side isolation circuit being balanced with said positive side isolation circuit and configured to provide transmission of broad band signals; a positive side transmitter electrically connected to said test instrument side of said coupling transformer and including a positive side driver, a negative side transmitter electrically connected to said test instrument side of said coupling transformer and including a negative side driver, a positive side receiver electrically connected to said test instrument side of said coupling transformer for receiving a signal from said first conductor of the line under test; and a negative side receiver electrically connected to said test instrument side of said coupling transformer for receiving a signal from said second conductor of the line under test.