Each of nodes in a communication system includes a pull-up circuit connected between a power source and a transmission line and a switching portion connecting and disconnecting the transmission line and a ground line. One of the nodes is a master node, and the others of the nodes are slave nodes. The driver circuits are driven so that the master node constantly outputs the transmission code of logic 1 and the slave node outputting the transmission code of logic 0 extends the width of the low level of the transmission code of logic 1 on the transmission line. The master node further includes a current limiting section limiting an electric current that flows to the transmission line via the pull-up circuit based on at least a signal level of the transmission line.