Patent ID: 7050434

Claim:
A digital transmission apparatus, which accommodates a plurality of terminals for exchanging asynchronous frames each including a MAC address, and is used for transmitting said asynchronous frames by putting each of said asynchronous frames in a synchronous frame, said digital transmission apparatus comprising: an address table for storing an address of a group including said digital transmission apparatus; a header-creating unit for creating a header including a communication-destination transmission-apparatus identification including said address of said group including said digital transmission apparatus; a header-adding unit for creating a first frame by adding said header to data of an asynchronous frame received from any one of said terminals; a frame-receiving unit for receiving a synchronous frame; a distribution unit for extracting a first frame from a synchronous frame received by said frame-receiving unit, comparing a communication-destination transmission-apparatus identification included in a header of said first frame with said address of said group including said digital transmission apparatus and forming a judgment as to whether to relay or accept said first frame in dependence on a result of comparison; and a frame-transmitting unit for transmitting a first frame created by said header-adding unit or passed on by said distribution unit by putting said first frame in a synchronous frame.