Abstract: In a communication system across an in-office PC system (10) and an in-enterprise LAN system (20), in order to perform a transmission of packet data from a DDTE (22) on the LAN side to a M-DTE (14) on the personal station side without a need of a provision of complicated means, when receiving packet data addressed to the M-DTE (14) from the DTE (22), a LAN side control unit (23) transmits a connection request including the incoming packet address to a PBX (11) of the in-office PC system (10), the PBX (11) notifies a PS (13) of the incoming signal for the packet address through a CS(12), and on the other hand, the M-DTE (14) connected to the PS (13) acknowledges the incoming signal through the PS (13) and the CS (12) when the packet address which received this notice corresponds to the M-DTE (14), thereby achieving a connection. After the connection, the control unit (23) transmits packet data to the M-DTE (14).

Abstract: In order for the user to perform a transmission of packet data to a desired communication counterpart on a virtual network across a wireless circuit exchange type network system and a LAN without being bothered by address exchange between an address of a physical network and an address of a virtual network, an exchange (10a) performs an address exchange necessary for establishing a communication channel between the terminal equipments within the system using a conversion table, in a mobile wireless data communication system in which a wireless circuit type network system comprising a wireless mobile station (30a), a wireless connection equipment (20a) and the exchange (10a) is connected to a LAN (40a) through a TA (60a) and a router (50a).