PURPOSE: To connect a lot of LAN equipments in series without the delay caused by equipment passage by providing a bypass path for directly linking each received signal line of a twist pair port to the transmitting signal line of another port.

CONSTITUTION: At the time of power source FF, in an MAU 10, relay circuits 7a and 7b directly connect pair ports 1a and 1b and output a received signal Rx as a transmitting signal Tx without delay. When a power source is turned on, the relay circuits 7a and 7b connect the pair ports 1a and 1b to selector function parts 6a and 6b and output the received signal Rx as the transmitting signal without delay. When an input signal Do is detected from an AUI port 2, MAU function parts 4a and 4b are connected to the relay circuits, the signal Do is outputted as the sending signal and even when the collision of signals is detected, a jam signal from a control circuit 3 is similarly sent from the control circuit 3 as well. Thus, the delay of signals is reduced by the passage through the LAN equipment, and an expandable/movable simplified network can be provided.