Abstract: A method and apparatus for transmitting digital data between subscriber stations and a subscriber concentrator and using time hybrids are described. The two-wire lines connecting the subscriber stations to a concentrator are utilized on a four-wire basis, and operate on a time interleaved manner of actuating the send and receive modes of operation of the time hybrids. The send mode of the time hybrid at the subscriber concentrator is actuated responsive to a synchronizing pulse from the concentrator. The send mode of the time hybrid associated with the subscriber stations occurs upon acceptance of data over the two-wire line and a specific time relationship is established between the received data and the initiation of the send mode. In both types of time hybrids a receive pause occurs between the send mode and the subsequent receive mode, and the pause is of a duration corresponding to the anticipated maximum transit time over the two-wire line.