TELECOM Digest OnLine - Sorted: Re: Telephone Area Codes and Prefixes

Re: Telephone Area Codes and Prefixes

Robert Bonomi (
Tue, 27 Feb 2007 17:36:03 -0000

In article <>, Ron Kritzman
<> wrote:

> wrote:

>> The other cool thing about that number is that it is of course the lowest
>> (generally-dialable) phone number in the entire world!

>> Fully qualified, it is +1 201 200 0000....

> In the telephony world 0 is a ten not a null, so wouldn't that be a
> pretty high number?

TELECOM Digest Editor then tried to use his diseased brain-thingy to
respond, with the usual predictable results:

> [TELECOM Digest Editor's Note: I think that all depends; if you are
> dial pulsing the number it is a 'ten'.

True for North American phone systems.

There are other, incompatible, phone systems that use different
encodings. One uses two through eleven pulses for the digits, with
'n+1' pulses for 1-9, and eleven pulses for '0'. This greatly reduced
false-digit detection from the equivalent of a 'switch-hook flash'.
Another (utterly obsolete, to the best of my knowledge) used inverted
pulse counts -- '0' was one pulse, and '1' was ten.

> if being 'tone dialed' is not known to me. Is it still considered a
> 'ten'. In that case, are the '*' and '#' keys considered eleven and
> twelve when dialed? PAT]

When tone-dialing,
first group: 1,2,3,'A'
second group: 4,5,6,'B'
third group: 7,8,9,'C'
fourth group; *,0,#,'D'

So, '0' could be considered a fourteen, with '*' and '#' being a
thirteen and fifteen. However, data-processing gear tends to use
index values starting with zero; thus '1' would have an index of zero,
'4' would have an index of four, '7' would have an index of eight, and
'0' would have an index of 13. With '*' and '#' having index values
of twelve and fourteen.

Basic tone-decoder chips put out 2 bits for which low-tone was
detected, and 2 bits for which high-tone was detected. There is
little to no point in 'translating' that nybble of data to any sort of
'display' representation (ASCII, EBCDIC, SIXBIT, FIELDDATA, or
'whatever') when it is being used internally by automation for

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