[Asterisk-Users] asterisk and pstn

[Kevin Brennan]

In simple terms ISDN is a digital interface to the PSTN as opposed to the
analogue RJ11 phone connectors your used to at home (POTS - Plain Old
Telephony System).  ISDN lines (Integrated Services Digital Network)
typically comes in two configurations BRI (Basic Rate has 2B+D channels ie.
2 speech 1 data ) and PRI (Primary Rate , (Europe)30B+D - 30 speech + 1
data). Because ISDN is digital the interface it's more advanced and supports
a much wider set of functions and services than POTS. In Ireland Eircom
market ISDN as 'hi-speed', you may be familiar with this (this is not ADSL,
your not always online). The main suppliers of this type of service would be
Eircom, Esat and COLT. Line rental for PRI will be in the order of €3K/month
plus a setup fee (yes - that puts the cost of the card in perspective).

To conect your * box to PSTN with BRI/PRI interface you'll need one of
digium's cards or an equivalent CAPI card.
Br /Kev/

----- Original Message -----
From: "Ashling O'Driscoll" <ashling.odriscoll at cit.ie>
To: <asterisk-users at lists.digium.com>
Sent: Wednesday, November 24, 2004 4:17 PM
Subject: [Asterisk-Users] asterisk and pstn


Hi,

First of all apologies because this isn't strictly a purely asterisk
question.

I am quite new to asterisk and actually to voip/telephony as a whole.
I currently have sip calls working through asterisk. The asterisk
server is behind a linksys router. I would now like to connect calls
to the pstn. I have researched into several ways to do this but
because I am not very knowledgeable about telephony I am now quite
confused. This is what i understand so far. If this is incorrect or
if anybody has any ideas as to I could implememnt this in a
better/more scalable fashion, I would really appreciate it.

I could put a fxo card in my asterisk server and connect this to a
telephone line. This would enable sip to pstn calls but only one call
at a time. To connect analog phones from the inside network(i.e. the
asterisk network) going out I would need an fxs card.

Now the problem with the above scenario is that only one call would
be allowed at a time. I know I could get an fxo card with a few ports
but that would still only allow a few calls. To implement a network
where several calls are possible then do I need a pbx with a PRI
interface?? Also where does all the digium cards come in all
this??Where do they fit in??

I would be extremely grateful if somebody could shed some light on my
currently very hazy understanding of voip telephony with asterisk

Thanks again,
Aisling.


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