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The state of California was divided into three numbering plan areas (NPAs) with distinct area codes: 213, 415, and 916, for the southern, central, and northern parts of the state, respectively. [ 1 ] In 1949, Oakland, CA, received the fifth regional dial switching center for Operator Toll Dialing in the nation, [ 2 ] which set the stage for ...
Area codes are also assigned for non-geographic purposes. The rules for numbering NPAs do not permit the digits 0 and 1 in the leading position. [1] Area codes with two identical trailing digits are easily recognizable codes (ERC). NPAs with 9 in the second position are reserved for future format expansion.
The Major Diagnostic Categories (MDC) are formed by dividing all possible principal diagnoses (from ICD-9-CM) into 25 mutually exclusive diagnosis areas. MDC codes, like diagnosis-related group (DRG) codes, are primarily a claims and administrative data element unique to the United States medical care reimbursement system. DRG codes also are ...
ICD-9 chapters; Chapter Block Title I 001–139: Infectious and Parasitic Diseases II 140–239: Neoplasms III 240–279: Endocrine, Nutritional and Metabolic Diseases, and Immunity Disorders
Classification System Detail ICD-9-CM: Volumes 1 and 2 only. Volume 3 contains Procedure codes: ICD-10: The international standard since about 1998 ICPC-2: Also includes reasons for encounter (RFE), procedure codes and process of care
The second area code, 202, was assigned to the District of Columbia. The allocation of area codes was readjusted as early as 1948 before the implementation of the plan commenced. For example, the Indiana numbering plan area 317 was divided, which essentially provided a larger numbering pool in the Indiana suburbs of Chicago (area code 219).
Telephone numbers in Puerto Rico are assigned under the North American Numbering Plan (NANP). Their area codes are 787 and 939.. Prior to March 1, 1996, Puerto Rico was one of many Caribbean islands served by area code 809.
Most of the Washington region's inner ring is a single local calling area, even though it is split between three area codes–the District's area code 202, Maryland's area code 301 and Northern Virginia's area code 703. For most of the second half of the 20th century, it was possible to dial any number in the metro area with just seven digits.