PURPOSE: To efficiently connect LANs by providing a function temporarily making a connection request by means of a packet switching channel when a line switching channel is busy and returning the used channel from the packet switching channel to the line switching channel when the line switching channel is made available.

CONSTITUTION: An ISDN network 1 supporting packet switching service and line switching service, LAN networks 100, 200,... 400, gateway equipments 110, 210,...410 and nodes 101, 102,...104,...401 and 402 on the LAN other than the gateway equipments are provided. Whether or not the line switching channel is available is first checked. When it is available, the line is connected and then disconnected after the completion of data transfer. When the line is not available, the connection by means of the packet switching channel is made and the data transfer is started. When the availability of the channel is detected, the packet switching channel is disconnected and the line switching channel is connected.