a communication data switching apparatus for use between an input line , an output line , and a memory bus includes a receiver connected to the input line , a transmitter connected to the output line , a buffer memory for storing data received by the receiver and data to be transmitted by the transmitter , a memory transfer controller for controlling transfer of data between the buffer memory and the memory bus , and a main control unit for controlling the receiver , the transmitter , the buffer memory , and the memory transfer controller to store a signal which has been received from the input line by the receiver , in the buffer memory , to transfer the signal to the memory bus , to confirm whether data on the memory bus are addressed to a station to which the main control unit belongs , based on the content of the data , and to deliver the data through said transmitter to the output line if the data are addressed to the station . the communication data switching apparatus can quickly distribute a received signal to a plurality of stations . a communication data switching system may include a plurality of such communication data switching apparatus .