The fundamental building block of the USA’s complex tariffing topology is the unit known as a LATA (Local Access and Transportation Area), which is computed from geographical distribution of population.
Some sparsely populated US states may contain only a single LATA, while the bigger ones contain several. In a few cases, a LATA may even encompass parts of two states. LATAs may contain one or several area codes.
‘Local calls’ in US terms are thus defined as calls made within one exchange, or between a group of exchanges situated in a single LATA. Intra-LATA calls are those made within a LATA, beyond the local calling area. At the next level up, Intra-state calls are classified as those made between LATAs and originating and terminating in the same state. Last of the categories, and thankfully the simplest, are the Interstate-calls. Self-evidently, these calls cross state boundaries.
All four call types – local, Intra-LATA, Intra-state and Inter-state – may be defined in some part by distance. Within each category of call, the number of tariffing zones used to price a call may be between four and 10. In addition, distance bands may also overlap, so that, for example, a call as short as 20 miles in length may be costed against as many as three different sets of rates.
Banding structures in Europe are rather simpler. With some minor variations between countries, local calls in Europe run, as in the USA, within one exchange or group of exchanges. But regional and long-distance calls are determined by distance alone. Distance in Europe is defined in reasonably broad and discrete (ie non-overlapping) bands – for example, 56Km in the UK. In contrast to the States, a long-distance call in Europe will typically be charged on the basis of one, or at most three, tariffing bands.
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