Rate center

In the North American Numbering Plan, a rate center (rate centre in Canada) is a geographically-specified area used for determining mileage and/or usage dependent rates in the public switched telephone network.^[1]

Unlike a wire center (which is the actual physical telephone exchange building), a rate center is a regulatory construct created primarily for billing purposes.

Each rate center is associated with:

• a geographical place name (city, province/state)
• a nominal physical location (V and H co-ordinates) for distance calculations for billing purposes
• one or more prefixes, in the form +1-NPA-NXX, which each identify a block of ten thousand directory numbers
• a specified local calling area, identified as a list of other individual rate centers to which local or flat-rate landline calling is provided

A rate center may contain one or multiple physical wire centers; conversely, it may merely be a legal fiction retained for billing purposes with its actual subscribers served from the same physical switch as an adjacent community.

A telephone number prefix (1+6 digits) normally suffices to uniquely identify a rate center; if number pooling and local number portability were not in use, it would also uniquely identify a wire center.

For instance, BUtterfield 8 (+1-212-288-xxxx) identifies a specific office (CLLI code NYCMNY79DS1, Verizon's building at 208 E 79th St, New York NY) as its default wire center^[2] but identifies "New York City, Zone 1" as a rate center.^[3] "New York City, Zone 1" includes multiple competing telephone companies operating various wire centers (for land line, voice over IP and mobile phone service) at multiple central offices across all of Manhattan's 212. These facilities are in multiple locations throughout the borough.