Digital Cross Connects(DXCs) handle signals of PDH and/or SDH technologies.They offer several inputs for those bitrates which are present as port cards in a specific hardware configuration of this network element.Today its possible to apply signals up to STM-4, in the future 2.5Gbit/s will bepossible.A cross connect extracts containers from all incoming signals. It can rout all incoming signals (or parts of them) to each outgoing signal, from one hierarcye to another, from SDH to PDH and vice versa.
Normally switching takes place at the basic container levels (VC12, VC3, VC4). Some DXCs offer access down to 64kbps by the help of byte-synchronous mapping.DXCs are located at such places where several different signals are coming together, with different bitrates. It also interconnects local levels to long distance levels, e.g. ADM rings on SLX or PDH on SLX. Its controlled via workstations and TMN and handles also all alarms and status information of different hierarchies.
A DXC requires fully structured signals (PDH 140/34/8/2Mbps) of the corresponding bitrate, otherwise it will generate alarms and measurements are more difficult or impossible.
DXCs are very complex machines - therefore the goal of most operators is to minimize the amount of DXCs and to replace them by the more cheeper Add Drop multiplexers (ADMs) wherever it's possible.
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