rsm@amethyst.ma.arizona.edu (Robert Maier) (08/05/88)
The following is taken from the 1980 edition of the former AT&T
publication ``Notes on the Network''.
[An] area of Mexico with a high community of interest with the
United States is Northwest Mexico, particularly the
Tijuana-Mexicali area. In 1963, NPA code 903 was assigned for
North American dialing to this limited part of Northwest Mexico.
Northwest Mexico is designated in Mexico's national numbering plan
as zone 6; consequently, the digit 6 becomes the first digit of
the 8-digit national number. In late 1980, the area served by NPA
903 was renumbered to conform with the Mexican numbering plan. To
continue North American dialing into Northwest Mexico and to be
consistent with the pseudo NPA scheme developed for Mexico City,
NPA code 903 was replaced by pseudo NPA code 70 (6).
Standardizing telephone numbering in this part of Northwest Mexico
made all of Mexico accessible in the IDDD [International Direct
Distance Dialing] format. Assigning code 70 (6) not only
standardizes the pseudo North American interim plan for Mexico but
expands the area served to include all of zone 6 in Mexico.
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Robert S. Maier | Internet: rsm@amethyst.ma.arizona.edu
Dept. of Math. | UUCP: ..{allegra,cmcl2,hao!noao}!arizona!amethyst!rsm
Univ. of Arizona | Bitnet: maier@arizrvax
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