
Falsehoods Programmers Believe About Phone Numbers - tonyg
https://github.com/googlei18n/libphonenumber/blob/master/FALSEHOODS.md
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DrScump
In the USA, not only did the area code used to be specific to a given
location, but the _prefix_ (first 3 of 7 digits) used to identify the _zone_
you were in within a prefix. Your "local" calling area (numbers you could call
without per-minute charges) was determined by your prefix and would include
numbers in prefixes that were within your zone. IIRC, a prefix was in your
local zone if any number within it was within 15 miles of any point of your
zone. Local phone books would list the prefixes that were local calls and
those that were in progressively farther zones (with corresponding per-minute
cost increases).

I set up cheap calling systems for nonprofits back then. Three well-chosen
calling points could cover all of the greater San Jose area (including
southern Fremont and up through Menlo Park) with purely local, free calls.

~~~
greenyoda
Back in the days when a large part of Usenet was implemented using dialup
modems and uucp, the routing was set up to optimize the cost of the calls:
machines called machines that were nearby to take advantage of free or flat-
rate calls, and when machines needed to make long distance calls they'd do so
after 11pm when the rates went down. Thus, it could take days for articles to
propagate to the edges of the network.

Also: Interesting discussion of this article from a couple of years ago:
[https://news.ycombinator.com/item?id=11321236](https://news.ycombinator.com/item?id=11321236)

