What is the difference between TSA and TSI?
A. Time Slot Assignment (TSA) allows for flexible assignment for add-dropped signals but not for through path signals. Once a signal is multiplexed onto a time slot it stays in that time slot until it is dropped. Time Slot Interchange (TSI) is more flexible in that it allows a signal passing through a node to be placed in another time slot if desired. Equipment that provides neither TSA or TSI is said to be hard wired. This pass-through grooming, which is not supported by systems limited to TSA, allows in-transit bandwidth rearrangements for maximum facility utilization. This grooming is most useful for networks with intersite routing (for example, interoffice or private networks) and networks with significant churn (service removal as well as new service installation).
