ON-VEHICLE COMMUNICATION LINE CONNECTION APPARATUS

Instead of a joint connector, a function substitution unit is attached to a position where a plurality of communication lines of systems of a wire harness are concentrated. The function substitution unit includes a plurality of terminals for connection of CAN buses of a plurality of systems, and detects and blocks an unauthorized signal sent from an unauthorized device by distinguishing a position of each terminal from a region of a path through which a CAN signal passes.