[Asterisk-Users] ATA's

[Stewart Nelson]

>>> Hi,  Has anyone had any luck using modems on ata's
>>> other than with Cisco ATA-188's?  I really don't
>>> have the money pay for the 188's as this is for my
>>> personal use.
>>> Thanks.

>> grandstream 486 should do.

> Should do or will do?  My boss (wife) will not be happy with me if it
> doesn't work.

Running analog modems over a VoIP connection is extremely problematic.
Your chance of success is far more dependent on network speed, delay,
jitter, packet loss, etc. than on the specific adapter you choose.

What is your application?  How does the IP get to the modem on
the other end?

If you have to use a compression codec, because your network
connection is too slow, or because your provider requires it,
then you are probably out of luck.

If you have lots of jitter, e.g. you are on a cable modem and your
neighbors like to file share, it is also unlikely to work.

Don't even think about V.90.  If your IP connection is to a
carrier that moves the media stream digitally, unchanged, to
the PSTN, and you're dialing into a digital modem bank, then you'll
probably connect V.34 at 9600 to 19200 bps.  If the path goes back
to analog at the other end, figure on 4800 to 9600.

Long ping times that exceed the modem's echo canceling ability,
e.g. on overseas calls, can greatly reduce the speed, or prevent
connection altogether.

If you will be making long calls, expect that they will
occasionally be dropped because of network congestion, and
you'll have to reconnect.

Even a little glitch during the initial negotiation and training
phases can cause you to get garbage -- you'll have to hang up
and try again.

If you are convinced that the ATA-188 will do the job, the less
expensive ATA-186 should do as well; the only difference is the
lack of an uplink port.  You can often find used ATAs on Ebay.
Just make sure that they weren't locked by Vonage :)

Your best bet would be to borrow an adapter, try it on your network
in your application, and see if it works.

--Stewart