A communications bus management circuit for a current probe system detects the connection of the current probe system to an instrument and the connection of a current probe to a current probe amplifier of the system. A controller generates a probe enable signal in the presence of the detected connection to the instrument that is coupled to a switching circuit. Switch elements couple the communications bus of the instrument to the communications bus of the current probe amplifier in the presence of the probe enable signal. The controller further generates a current probe present signal in the presence of the detected current probe that is also coupled to the switching element. A further switch element couples the data line of the instrument to ground via a resistive element in the presence of the current probe present signal and floats the data line when the current probe present signal is absent.