On 2/28/07, Nate Carlson <tclug at natecarlson.com> wrote: > On Wed, 28 Feb 2007, Dave Sherman wrote: > > The T1 cards with hardware echo cancellation were a lifesaver for us, > > not sure if any other manufacturers are producing a card with that > > feature. > > I know Sangoma also makes one. They also do a lot more in hardware (ie - > the price tag skyrockets). I'll have to look into those -- any idea how they compare with Digium, in "bang for the buck"? > > Can't say much about the FXO/FXS cards from Digium, besides the fact > > that they work as expected. We have used them for testing, but do not > > have any in a production server. > > Avoid the FXO/FXS cards whenever possible. :) Yeah, in our environment, the only place we would use them is for integration with an older PBX -- which is exactly what we were testing. We are unable to add a 2nd T1 card to the PBX, so we used a CO card and connected it to the FXO ports on the Digium card. > My advice would be to get digital trunks (BRI's or PRI's), and if you need > FXS ports (for fax machines, door phones, etc), get a channel bank to > split a T1 into multiple analog lines. If you can't get digital lines, you > can get channel banks that will let you configure (for example) 16 ports > as FXO and 8 ports as FXS - so you could plug 16 analog phone lines into > it, and 8 analog extensions. If Eric is already spending $300/month or more on 8 analog lines, a BRI line could be very cost-effective, making this is a good suggestion. > > The biggest challenge we've had is with faxing. We ended up bringing in > > dedicated analog lines from Qwest for our faxes at one installation, but > > faxes at the other installation are running off Sipura (now Linksys) > > SIP-to-analog converter boxes, and they seem to work fine -- but they > > also use the faxes less than the folks who got analog lines. > > Have you tried the fax support for Asterisk (or OpenPBX)? I've heard good > things about it; haven't ever tried it, though. We tried it (using the latest version of asterisk compiled from source), but to be honest, hit a wall when Asterisk would core dump every time a fax came in. Since we were under a bit of time pressure (to put it mildly), we went the "easy route" and just got a couple of analog lines from Qwest. This is something we definitely want to investigate in the near future, though, since it would save us a bit of cash, and add some nice functionality to the system. Every DID can become an instant "fax machine", effectively giving each office user their own personal fax. > > I do seem to recall reading that having more than one card in a single > > server can lead to performance issues, because the telephony interface > > cards tend to generate so many interrupts on the system bus, and they > > need to run in real time -- if you have too many cards, it will start to > > show in performance rather quickly. > > The Sangoma cards solve this - the cards don't generate a pile of > interrupts. Good to know. They must keep a lot of processing in the card itself, rather than sending it to the CPU, right? Otherwise I can't see how this would work. -- Dave Sherman MCSA, MCSE, CCNA Linux: Because rebooting is for adding new hardware.