[c-nsp] analog to digital

[Jonathan Charles]

Here's the thing.

FXO ports are expecting to receive dial-tone, FXS provide it.

So, the line from telco plugs into an FXO and a phone plugs into an FXS
port.

For any of these to be recognized by the router you are going to need DSPs
(in the form of PVDMs).

So, it really depends on what you want to do.

If you have IP phones, then you just need FXO ports (you can get a VIC-2FXO
card for a 1760 on Ebay for about $100), and you can get PVDMs (a PVDM-8,
will cover you pretty well for analog on a 1760, for about $100).

The DSPs turn the analog waveform and sample (eight thousand times a second,
generally) and put that waveform into IP packets (usually with 20ms of voice
per packet) via an audio codec (usually G.711 or G729a).

Without DSPs, two things happen.

First your router will not see the voice ports (not even know they are in
the box), second, you wouldn't be able to packetize voice without them. So,
they are necessary.

Some hardware modules have DSPs on them (the NM-HDV for example), but most
do not.

The working assumption is that that you will scale your DSPs to meet your
needs (they do more than JUST packetize analog audio, they can also provide
transcoding services, conferencing, and act as a media termination point
(for putting people on hold).



Jonathan


On 12/20/06, George Sobhi <gsobhi at nileonebrokers.com> wrote:
>
>  Dear Jonathan,
>
> Are FXO and DSP different? And if I purchased FXO do I need to purchase
> FXS also???
>
> Thanks & regards
>
>
>  ------------------------------
>
> *From:* Jonathan Charles [mailto:jonvoip at gmail.com]
> *Sent:* Wednesday, December 20, 2006 3:49 PM
> *To:* George Sobhi
> *Cc:* Kevin Graham; cisco-nsp at puck.nether.net
> *Subject:* Re: [c-nsp] analog to digital
>
>
>
> Well, one way or another, you are going to need ports to plug the lines
> into and you are going to need DSPs, there really isn't a way around it.
>
>
>
> Jonathan
>
> On 12/20/06, *George Sobhi* <gsobhi at nileonebrokers.com> wrote:
>
> Dear Kevin,
> Sorry I mistyped my router is 1760 and if there is a way to do that
> without
> purchasing any hardware??
> Thanx and regards
> -----Original Message-----
> From: Kevin Graham [mailto: mahargk at gmail.com]
> Sent: Tuesday, December 19, 2006 6:40 PM
> To: George Sobhi
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] analog to digital
>
> On 12/19/06, George Sobhi < gsobhi at nileonebrokers.com> wrote:
> >
> > How can I figure the PSTN analog line to 2700 Cisco router?
>
> Atleast one of those numbers is wrong -- 2700 doesn't exist, perhaps
> one of 1700, 2600, 2800, 3700? Either way, what you're looking for is
> an FXO interface; with that, and the right model number the
> appropriate part should be easy to chase down on CCO.
>
> _______________________________________________
> cisco-nsp mailing list  cisco-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/
>
>
>