[asterisk-users] Extension Numbering

[John Marvin]

Norbert Zawodsky wrote:

> <quote>
> ... (Well, almost. Extensions must be shorter than 80 characters long,
> and you shouldn’t use single-character extensions for your own
> use, as they’re reserved.) ...
> </quote>
> 
> O.k. - This answers my first question ("if there is disadvantage if we
> use only 1 digit extensions").
> But what for are single-character extensions "reserved" ?

As others have mentioned the single "character" extensions are reserved 
for special extensions in the dialplan, i.e. 's' for start, 't' for 
timeout, 'i' for invalid, etc.

However, the single "digit" extensions are not reserved, so you can use 
them if you want. The only problem with using single digit extensions is 
the reduced flexibility in your dialplan, i.e. things like: 1) no room 
to expand your number of extensions without having a mix of 1 digit and 
2 (or more) digit extensions, 2) having to have a prefix number for 
dialing an external number, etc.

Of course, if you don't have a dialout digit (e.g. '9') then you have 
limited flexibility also. Since I don't have a dialout digit and I allow 
both 7 digit (NXXXXXX) and 11 digit (1NXXNXXXXXX) dialing, I don't have 
that many options for extensions either (they either have to start with 
10, 11 or 0). Right now I'm using three digit extensions starting with 
10 and 11 (i.e. 10X and 11X) but I am running out, and am thinking of 
moving to three digit extensions starting with 0 (i.e. 0XX, except 011 
would still work for international dialing). I don't have any use for 
just 0, since I don't even know what dialing an operator should mean in 
the context of a mixed PSTN and multi provider VOIP setup (not to 
mention I haven't called an operator of any type in over 20 years).

John