RELAY CONTROL SYSTEM

PURPOSE:To eliminate bottle neck of transmission by a host for relay by registering plural codes representing contents of data received by each terminal device connected to each loop transmitting line to a memory in each terminal device respectively so as to relieve the load of the host for relay. CONSTITUTION:When a transmission data from a host 100 is received via an interface 55, a transmission controller NCP10 stores it to a buffer 56. When a processing operating device 52 identifies that a content code FC of the stored data is an FCr representing the registration of the received FC, a data in the buffer 56 is read and registered in a receiving FC memory 59. When a data is stored in a buffer 51 from a loop transmission line 1 via an interface 50, the processing operating device 52 reads the FC part and identifies the FC registered in the receiving FC memory 59, i.e. the FC where d1-dN are logical 1, the contents of the buffer 51 are copied in the buffer 57 and transferred to the host 100 via the interface 55.