From: TONY@VM1.MCGILL.CA (Tony Harminc)
Newsgroups: comp.dcom.telecom
Subject: Re: N0N/N1N Exchanges and 1+ Dialing
Date: 30 Sep 92 23:55:29 GMT
Organization: TELECOM Digest
X-Submissions-To: telecom@eecs.nwu.edu
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X-Telecom-Digest: Volume 12, Issue 750, Message 1 of 13

deej@cbnewsf.cb.att.com (david.g.lewis) wrote:
 
> 1.  The 1+ can be required for 10-D calls, and required to be absent
> for 7-D calls.  The 1+ is therefore the indicator to the switch to
> expect ten following digits.  This is called the "prefix method".

> 2.  The 1+ is "optional" from a dialing point of view (e.g. is used to
> indicate local/toll).  A four-second Final Digit Timer is started
> after seven digits are received.  If this timer times out, the switch
> interprets the number as 7-D; if a digit is received before the timer
> times out, the switch expects a 10-D number.  This is called the
> "timing method".

> 3.  The 1+ indicates local/toll, and the switch examines the three
> digits following the initial 1.  If they are an N0/1X which is not
> assigned as a CO code in the NPA, they are interpreted as an NPA code
> and seven more digits are expected.  If they are an N0/1X code which
> is assigned as a CO code in the NPA, a Final Digit Timer is started
> after four more digits are received, as in the timing method.  If they
> are an NNX code, only four more digits are expected.  This is called
> the "hybrid method".

> Bellcore recommends the prefix method as the standard dialing
> procedure.
 
There seems to be a fourth method which avoids all the problems, as
far as I can see: simply avoid using for CO codes any NPA codes that
contain locally-callable numbers.  I believe this is exactly what is
going to be done when 416 splits to 905 next year.
 
So (from a 416 number):
 
486-nnnn                 a local call within 416
905 477-nnnn             a local call to a 905 number
1 905 468-nnnn           a toll call to a 905 number
905 468-nnnn             recorded warning - "please dial 1 first"
905-nnnn                 no such number - times out to recording
416-nnnn                 no such number - times out to recording
1 416 234-nnnn           a toll call within 416 (actually there won't be any)
212-nnnn                 a local call within 416
1 212 456-nnnn           a toll call to a 212 number
 
No timeouts (ugh!) are necessary.  1+ means "toll call", which many
people like (I don't want to reopen that whole argument).  The telco
can (and I think should) allow 1+ for local calls too without problem.
 
Now if 416 splits again in a few years, and (say) new style NPA code
260 is assigned and some numbers within 260 are a local call from 416,
then the only numbering restriction is that 260 must not be assigned
as a CO code within 416.  This can be planned for a long way ahead.
 
260 439-nnnn            a local call to a 260 number
1 260 687-nnnn          a toll call to a 260 number
 
How many area codes (even with overlays) can be within the local
calling area of one city?  Five is pushing it.  Ten is almost
certainly not going to happen within the life of the NANP.
Restricting a handful of CO codes from assignment seems a pretty small
penalty to pay for consistency.

 
Tony H.