switching center
The term switching center (VSt) is used in public long-distance networks. It is the facility that provides the switching technology for a Tk network and carries out the connection process. Switching centers include those for circuit switching and data packet switching.
In telephone networks, exchanges are structured hierarchically. The lowest hierarchical level in long-distance networks is the local exchange. Above the local exchange is the node exchange(KVSt), above that the main exchange(HVSt) and at the highest hierarchical level the central exchange (ZVSt).
This hierarchy is not mandatory; in geographic areas with low population density, one switching level may be omitted and switching may be handled by the lower level. The generally applicable, network-independent term for such a network component is node.