Patent ID: 6473397
Filing Date: 2002-10-29
Classification: H04L,H04Q

Abstract:
An add/drop multiplexer comprising:a plurality of service terminating units (STUs) each having an associated identifier operable to receive information units from external services and converting these into switching units containing a destination identifier, and to receive switching units having the associated identifier and combine them into information units and output them to the external services; a switching component having a first set of dedicated receive ports operable to receive working channel traffic, a first set of dedicated transmit ports operable to transmit working channel traffic, a second set of dedicated receive ports operable to receive protection channel traffic, a second set of dedicated transmit ports operable to transmit channel traffic, and an STU port for each STU operable to receive switching units from the respective STU and to send switching units to the respective STU; wherein switching units received by the switching component from the STUs are output through the first set of dedicated transmit ports unless a protection event has occurred affecting those ports in which case the switching units are output through the second set of dedicated transmit ports; and wherein the destination identifier of each switching unit received by the switching component from the first set of dedicated receive ports is examined by the switching component, and if the destination identifier is the same as the identifiers associated with one of said STUs, the switching unit is passed to the one of said STUs, and otherwise the switching unit is output through the first set of dedicated transmit ports unless a protection event has occurred effecting those ports in which case the switching unit is output through the second set of dedicated transmit ports.