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From: mcb@ihnp4.UUCP
Newsgroups: fa.telecom
Subject: 10XXX + 1 +
Message-ID: <85.10.02.0734.000@ihlpm>
Date: Wed, 2-Oct-85 08:34:00 EDT
Article-I.D.: ihlpm.85.10.02.0734.000
Posted: Wed Oct  2 08:34:00 1985
Date-Received: Fri, 4-Oct-85 03:09:05 EDT
Sender: daemon@ucbvax.ARPA
Reply-To: telecom@ucb-vax.arpa
Organization: The ARPA Internet
Lines: 29

> A related question:  Why is it that some areas insist that you dial 
> 10nnn 1+??  Here in Jersey, if you dial 10nnn and the number you want, you
> get a recording that you must "first dial a 1".  I thought that 1+ was 
> implicit in 10nnn+.  Down in DC, where I was last weekend, 10nnn+number
> works just fine in some areas, but others want the redundant 1.

In some areas (areas referring to area codes) all calls outside the area
code require 1+ 10 digits.  All calls within the area code require 7
digits only.  In other areas, all local calls are 7 digits, all TOLL
calls (inter- or intra-lata) are 1+ 7 or 10 digits.  In the latter case
the central office knows if you are going to dial 7 or 10 digits based
on the second digit.  Area codes have a 0 or 1 as their second digit.
Office codes have 2-9 as their second digit.  So much for the past...

In the last two years areas have run out of office codes, e.g. 312,
Chicago.  In these areas, 3 digit numbers formerly reserved as area codes
are being used as office codes.  The central office still needs to know
whether or not you are going to dial 7 or 10 digits.  The alternative
is that the CO has to wait 4-5 seconds after you dial the 7th digits 
just in case you were going to dial 10 digits.  This would upset many
people.  The way the CO predetermines if you are going to dial 7 or
10 digits is by the existance of the 1+ prefix.  This has to apply
to 10XXX calls also, since they can be 7 or 10 digits.  And that is why
some areas require 10XXX + 1+ and some do not.

-- Mark

P.S.  MY work phone number is 312-510-xxxx.  510 used to be reserved
for future a area code.