long distance network
The classic long-distance network is a hierarchically structured network whose exchanges are interconnected in a linear fashion. It consists of several exchanges, which are collectively referred to as a long-distance exchange.
In thehierarchy of exchanges, the node exchange(KVSt) is located above the local exchange, above it the main exchange(HVSt), and at the highest level of the hierarchy the central exchange(ZVSt).
This hierarchy is not mandatory; in geographical areas with low population density, one switching level can be omitted and switching can be handled by the lower level. For this purpose, the exchanges are meshed with each other.
Each switching hierarchy can be assigned another digit of the area code: For example, if the area code is 02271, then the digits 02 are assigned to the central exchange, 022 to the main exchange, 0227 to the node exchange, and 02271 to the local exchange.