SYNCHRONIZING THE TRANSMISSION OF DATA VIA A TWO-WAY LINK

Transmission is synchronized in a cell based switch of user cells which can include different numbers of data bits. The transmission is performed via a two-way link between functional entities which each includes a link control function containing functions for starting and controlling transmission of data on the link by sync cells which are exchanged between the link control functions. The exchange of sync cells is controlled by a sync state machine having three states. In a HUNT state, the link control function investigates a sync cell coming in from the link for establishing whether it agrees with a predetermined pattern for sync cells. In a PRESYNC state that starts after a sync cell contains the predetermined pattern has been found in the HUNT state, the link control function investigates a predetermined number thereafter incoming consecutive sync cells for establishing whether they contain the predetermined pattern. If this is not the case, the control process returns to the HUNT state. In a SYNC state that starts after the predetermined number of sync cells containing the predetermined pattern has been found in the PRESYNC state, transmission of data on the link is admitted while supervising data with respect to faults. If faults are found the control process is started again in the HUNT state.