Abstract: In an interface module for connecting user terminals of the carrier sense multiple access collision detection (CSMA/CD) local area network (LAN) to a different access mode switching network, a transmit buffer is connected at one end through a transmit data channel to a user terminal and connected at the other end to a desired swtching system. A receive buffer is connected at one end to the switching system to store a receive packet supplied from it. An OR gate is provided having a first input connected to the transmit data channel, a second input connected to the other end of the receive buffer and an output connected through a receive data channel to the user terminal. A detector circuit detects when a transmit packet is received from the user terminal.