Abstract: A sensor capable of being coupled to a transmission line and monitoring a foreign voltage on the transmission line includes a voltage monitoring circuit. The voltage monitoring circuit is adapted to operate in a foreign voltage detection mode in response to receiving a first logic signal and a foreign voltage measurement mode in response to receiving a second logic signal. A method for operating a circuit to detect and measure a foreign voltage on a transmission line includes providing a first logic signal to configure the circuit to detect the foreign voltage. The foreign voltage is detected on the transmission line in the circuit. A second logic signal is provided to configure the circuit to measure the foreign voltage, and the foreign voltage is measured.