LINE CONNECTION DEVICE FOR DATA TRANSMISSION

PURPOSE:To improve the transmission efficiency when an error takes place by allowing a master station and a slave station to use a timer respectively and applying time division to the interval of transmission and reception to take synchronization for each station. CONSTITUTION:Each of a master station 1 and slave stations 21-23 is respectively provided with a timer counting time for synchronization with time division. When an error takes place in the slave station 22, since no connection acknowledge signal is sent to the master station 1 between prescribed times t2 and t3 of the timer, no carrier is in existence between the times t2 and t3 of the timer, the master station 1 and the slave stations 21, 23 discriminate it that the error takes place in the slave station 22 to send the connection acknowledge signal because no carrier is in existence. Then the master station 1 transits to the re-transmission state of a connection request signal and the slave stations 22-23 transit to the standby state from the master station 1. That is, when the master station 1 and the slave stations 21-23 make carrier sense and receive no connection acknowledge signal, it is discriminated to be the occurrence of an error and the master station 1 sends again the connection request signal, then the time for the retransmission of the connection request signal is decreased and the transmission efficiency is improved.