A tool bus spans multiple segments of a bottom hole assembly (BHA) is implemented as a transmission line with only a single electrical contact (SEC) across joints of adjacent segments. A common mode (CM) choke on the transmission line promotes return currents to pass through the transmission line as opposed to through parallel return paths and stabilizes the characteristic impedance on the transmission line. The tool bus uses a two-layer bus with a first layer that is used to communicate across segments and a second layer that is used to communicated among nodes within one segment. A primary node is used to link the primary bus and the secondary bus. A CM choke may be used at the connection between the primary node and the primary bus, at the connection between the primary node and the secondary bus, and/or at the connection between the secondary bus and a secondary node.