US Patent 7085114 Current direction detection

An electrical circuit is provided for detecting direction of a current flowing on a line, in particular of a bus of a test equipment. The circuit comprises a sense resistor coupled within the line. A first comparator is connected with its positive input to the line on one of the two sides of the sense resistor and with its negative input connected to the line on the other one of the two sides of the sense resistor. A second comparator with one of its inputs is connected to the line on one of the two sides of the sense resistor and with the other one of its inputs is provided with a voltage divider. Said first comparator provides an output signal depending on the direction of the current flowing on the line, and said second comparator provides a second output signal defining whether the first output signal is valid or not.