[Asterisk-Users] PSTN and Asterisk

[brett-asterisk at worldcall.net]

Vassili Gontcharov wrote:

> Hi quys,
> I look for a solution for interconnection beetwen PSTN and VoIP.
> My application have to treat few protocols comming from PSTN lines and 
> mixing data , dtmf and voice.
> Can I use Asterisk for :
>  
>  
> PSTN ----------> Asterisk (converting analog call to IP) ----------> 
> MyApplication  ( translation protocols and do some works with 
> incomming data)
>  
> What hardware I can use for this?
> Do use Asterisk G.711 protocol?
> Thanks 
> Vassili           
>  

Asterisk does this. There are T1/E1 cards and POTs cards. Asterisk is a 
pretty low-cost way of doing this. Most alternatives are pretty pricy 
and not very fleible, however, it all depends on your application. If 
you are supporting hundreds of users, asterisk is great for that.. 
thousands of uses, Asterisk can handle, but it gets messy (and you'll 
probably need to use SER as well.. depending on taste..). Tens of 
thousands.. well asterisk will have it's place, but you'll need to think 
about an carrier grade PSTN gateway and let Asterisk just do some of the 
voip stuff (registrar, voicemail, etc).

G.711 is good to use if you have no bandwidth constraints. I like to 
say, "you're going to pay for it somewhere" meaning you'll either pay 
more money for the bandwidth and less for processing power and computers 
with G.711 or you'll pay more in computers/processing power and less in 
bandwidth with fancy low bit rate codecs. My personal feeling is that if 
you leave it G.711, there are no sound degradation issues, DTMF issues, 
Fax issues (possibly with LANs or well connected/maintained WANs), Less 
computers to manage, more bandwidth to "do stuff with". If you introduce 
transcoding, the growth capability of the network is much less Linear 
because you just don't know what requirements will be made of the 
system. However, all that said, asterisk is very slick with transcoding. 
It does it very well.

-Brett