PURPOSE: To transfer consecutive data, by increasing the clock frequency given to a universal asynchronous receiver transmitter (UART).

CONSTITUTION: A transmission from a start-stop terminal 4 is received at a period T4 of a UART6, it is superimposed on a high speed line in a period T9 at an MODEM2 and transmitted to a start-stop synchronizing terminal 5 after being the synchronizing time T10 at a UART7. In this case, the condition among the periods, T4≥T9≥T10 are required. Similarly, the similar conditions can be tstablished for the start-stop synchronizing terminals 4 and 5. Generally, the transmitter clock frequency of the UART is 16 times the portrate at terminal, but the required conditions can be satisfied by taking 16 times +α for the transmitter clock.