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

Re: Telephone Area Codes and Prefixes

Neal McLain (
Tue, 27 Feb 2007 22:26:24 -0600

I wrote:

> So how would they pronounce 201-200-0000?

Bob Goudreau wrote:

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

Ron Kritzman wrote:

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

PAT wrote:

> I think that all depends; if you are dial pulsing the number it is a
> 'ten'.

Robert Bonomi wrote:

> 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'.

You may be thinking of Sweden.

But note that on the Swedish dial, zero is encoded as one pulse, not
eleven. Of course, that would still prevent wrong numbers due to
false-digit detection: the caller would get the operator.

Assuming, of course, that "false-digit detection" is actually a
problem. I always thought it was, but our friend Wes Leatherock
thinks otherwise. Wes?

PAT continued:

> Exactly how it [digit zero] is translated 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]

Tone dialing is accomplished by transmission of two audio tones within
the 300-3000 Hz voice bandwidth; hence the terminology "dual-tone
multi-frequency" (DTMF) signaling. Each digit (including *, #, A, B,
C, and D) is encoded by a different combination of a set of eight
audio tones. Digit zero is encoded as 941 Hz + 1336 Hz.

No matter how we encode numeric digits, we have to assign *something*
to represent zero. We can't represent zero by nothing at all
(although I've been told that Roman numerals don't have a zero). Over
the centuries, we humans have evolved numerous conventions: 0, 000,
0000, 0x00, "zero", "oh", "null", "nought", "goose egg", "zilch",...

In the telephony world, zero can be encoded as one pulse, ten pulses,
eleven pulses, 941+1336 Hz, or whatever. But for the purposes of
assigning human-readable telephone numbers, a zero is a zero is a

Therefore, I agree with Goudreau: 201-200-0000 is the lowest
(numerically) in the NANP.

And I suppose that:

- If you're counting dial pulses, the lowest would be 212-221-1111
(except that it might be tied with 212-212-1111 if the Illinois
Commerce Commission were assigning NNXs in New York).

- The highest (numerically) would be 989-999-9999, in an unassigned
NPA-NNX in Michigan.

- The highest (counting dial pulses) would be 909-900-0000, an
unassigned number in the Fantana, California rate center.

Neal McLain

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