| NPA | CHAR (3) | Numbering Plan Area code, the first three digits of a 10 digit North American Numbering Plan (NANP) number, commonly called the Area Code. |
| NXX | CHAR (3) | Central Office Code, the first three digits following the Area Code in a 10 digit NANP number, commonly called the telephone exchange or prefix. |
| BLOCK_ID | CHAR (1) | The 7th digit in a 10 digit NANP number which identifies the 1,000 block. |
| TBP_IND | CHAR (1) | Thousands-block pooling indicator. |
| LATA | CHAR (5) | 3 or 5-digit Local Access and Transport Area (LATA) code. 5-digit LATA codes are used in Florida only, the last two digits are the LATA sub-zone which represent Equal Access Exchange Areas (EAEAs). |
| LTYPE | CHAR (1) | Identifies whether the primary use of the NPA NXX is wireless or landline based on its initial assignment. |
| CONTAM | CHAR (1) | For pooled numbers, specifies whether the thousands-block allocation is contaminated (i.e. the block contains at least one number that cannot be assigned). |
| STATE | CHAR (2) | State or province postal abbreviation of the Rate Center locale. |
| COUNTRY | CHAR (2) | ISO 3166-1 Country Code of the Rate Center locale. |
| WC | VARCHAR (128) | Name of the Serving Wire Center, also referred to as the Wire Center, Central Office, or exchange. Decoded from the first 8 characters of the switch CLLI code, this field will identify at a minimum the city location of the telco switch. The Wire Center identifies where service for a particular NPA NXX originates from which may be different than the NPA NXX service area. |
| SWITCH | CHAR (11) | The Common Language® Location Identifier (CLLI) code of the telco switch serving the NPA NXX. This field is generally present for all United States and Canadian records but may be empty for certain Caribbean NPA NXX entries. |
| RCSTATUS | VARCHAR (2) | Specifies whether Number Pooling is required within this Rate Center. Currently applies to United States entries only. |
| RCTYPE | CHAR (1) | Identifies whether the Rate Center is a zoned or non-zoned Rate Center. |
| RC | CHAR (10) | Industry standard Rate Center Name Abbreviation. |
| TZ | CHAR (2) | Time zone of the Rate Center locale. |
| DST | CHAR (1) | Specifies whether daylight savings time is recognized. |
| ZIP | VARCHAR (5) | 5-digit United States ZIP or 3-character Canadian Forward Sortation Area code for the Rate Center locale. |
| ZIP2 | VARCHAR (5) | Second possible ZIP or FSA code |
| ZIP3 | VARCHAR (5) | Third possible ZIP or FSA code |
| ZIP4 | VARCHAR (5) | Fourth possible ZIP or FSA code |
| FIPS | CHAR (5) | United States FIPS county code or Canadian Census Division code. |
| FIPS2 | CHAR (5) | Second possible FIPS or Census Division code |
| FIPS3 | CHAR (5) | Third possible FIPS or Census Division code |
| CBSA | CHAR (5) | United States Core Based Statistical Area (CBSA) or Canadian Census Metropolitan Area (CMA) code. |
| CBSA2 | CHAR (5) | Second possible CBSA or CMA code |
| MSA | CHAR (4) | Historical 4-digit Metropolitan Statistical Area (MSA) code of the MSA the Rate Center is located in. MSA codes have been replaced with the 5-digit CBSA codes. |
| PMSA | CHAR (4) | Historical 4-digit Primary Metropolitan Statistical Area (PMSA) code of the PMSA the Rate Center is located in. PMSA codes have been replaced with the 5-digit CBSA code. |
| LATITUDE | DOUBLE | Latitude in decimal degrees of the general exchange location. |
| LONGITUDE | DOUBLE | Longitude in decimal degrees of the general exchange location. |
| OCN_CATEGORY | CHAR (1) | Identifies the general company/carrier "type" of the OCN. |
| OCN | CHAR (4) | Four-character NECA Operating Company Number. For non-pooled numbers, specifies the Central Office Code holder. For pooled numbers, specifies the LERG Assignee or block holder. |
| DERIVED_FROM_NPA | CHAR (3) | Indicates the previous NPA that existed in the area covered by a given NPA. In cases of overlays, some or all of the previous NPAs may still cover the area. The OVERLAY field should be referenced to determine how to interpret this field. |
| NEWNPA | VARCHAR (20) | Specifies the new area code to be used with the NXX or new area code(s) created in the same coverage area as the current area code. The OVERLAY field should be referenced to determine how to interpret this field. |
| OVERLAY | CHAR (1) | Single character field to determine how the DERIVED_FROM_NPA and NEWNPA fields should be interpreted. |