Any Suggestions

Hi, I have a customer that has two different BRI - ISDN connections.

They are tied into a contract which means they have to receive incominging calls via one BRI line, we are then going to install a new BRI ( Via UK BT ) and make all outgoing calls on these new lines.

My plan is to install a cheap OpenVox B100E BRI card to use incoming calls and a Patton SN4120 ( our prefered gateways ) for outgoing calls.

The only thing is i have never set a system up using multiple gateways.

Is what i have suggested above OK, would anyone recommend different hardware, the OpenVox card will only be used for around 14 months so we don’t want to spend a huge amount of money on this gateway. The only other thought I had is getting a better gateway and configure 2 lines as inbound only and the other 2 as outbound ONLY but to be honest i’m not sure a Patton gateway can do this.

Also, never used OpenVox kit before, is it supported with FreePBX ?

Any suggestions would be gratefully received.


I’ve just installed a system in the UK with 3xISDN-BRI circuits using a Sangoma A500. Works very well. Why not using something like the Sangoma with 1xdaughter board. The card has three connection on the rear each of which has a Y-cable to connect to two ISDN-2 circuits.

However why are you installing a second ISDN-2? Why not use a SIP trunk for the outbound calls rather than have to install the ISDN-2 line. I believe installation of the ISDN-2 is about £249.00 with monthly rental costs of £27.00. A SIP trunk would be cheaper and more flexible as once the other ISDN-2 can be cancelled you can just move the BT number on the ISDN-2 to the SIP trunk and be done with old ISDN technology for good.

Hi Lee,

Thanks for the info, much apreciated. I did consider a Sangoma as i have used them before but i HAVE to be able to ensure 1 set of ISDN lines are inbound and the other outbound hence why i thought two seperate gateways would be better. Sangoma have the same issue as Patton, i do not think you can sepeate the channels to congiure 2 as inbound ONY and the other 2 as outbound. Based on experience with Sangoma and Patton the Patton wins hands down… simular cost, better kit PLUS it is completly independandt of the server, i.e. the Gateway can be located in a diferent room to the server and operates via your LAN.

Regarding SIP connections… have you used them in the UK, if so have you had good feedback ?

We do utalise SIP lines for remote workers / remote office but i would never use them for customer related calls. With DSL connection’s you can not implament QOS due to not being able to guarantee your upload speed ( contention issues etc ), specially during school holidays. Also regarding cost, ISDN - free install with 5 year contract / £99.00 on 3 year contract, monthly cost is £15.00 per channel / £30.00 per ISDN2 connection. ADSL - dedicated PSTN line, same install charges, monthly cost @ £15.00 per month, plus ADSL costs @ £20 plus for a decent business connection ( non centended are alot more )…Plus SIP trunk costs ( if you want a decent connection NEVER use free carriers ). You really need around 60k - 90k per call upload and most ADSL conection are only 200 - 300k upload. So really 2 / 3 calls MAX. Cost of 2 SIP trunk’ per month - £35.00 per month infrastructure plus SIP trunk costs, cost of ISDN2 ( 2 lines ) £30.00 per month… Guaranteed good quality calls… In the UK at the moment… no contest…


You can use a Sangoma card or any other card with multiple connection to segregate inbound/outbound calls. Just make sure you put the different channels into different DAHDI groups. Do you really want to be stuck into an ISDN contract for 3-5 years?

I have used SIP connections very successfully over ADSL and SDSL. I now used Spitfire for SIP connectivity. Their SIP Trunk ADSL links are not standard Internet connections. They go into their private MPLS cloud allowing them to guarantee call quality. One ADSL circuit can support up to 4 SIP trunks with guaranteed voice quality.

Install of an ADSL2+ circuit with 4 SIP trunks is about £164.00+VAT (equivalent to 2xISDN-2).

Monthly cost is about £48.00+VAT (inc. the cost of the analogue line which you might want anyway for other applications such as fax or modem). This includes 4 SIP trunks with quality guarantee. I’ve installed a few of these now very successfully.

SIP trunks also have a host of other benefits include much more flexible disaster recovery and moving of lines to other locations without loosing your numbers.

So Spitfire copied my idea! Is it really MPLS? ADSL uses ATM for transport.

We do the same thing in Cleveland, we have an ATM OC-12 UNI interface to the AT&T DSL network. We terminate our PPPoE connections from our routers via this 655M link.

I am surprised they are not running g.729. We can get a whole PRI on an 512K Internet circuit. We install a Cisco router with a ADSL WIC and a Multiflex T1 for the PRI, it’s a popular product. Gives legacy operators a way to jump on the SIP bandwagon.

Yes as far as I understand it is MPLS. It seems to work pretty well. One thing I am not happy with is that they don’t support G.729. I would be much happier if they did. As you say you can get a whole load more calls down an ADSL using G.729. But they don’t support it. I went with Spitfire in the end because I had tried various Internet based ADSL services (including some rather expensive services claiming to be tune specifically for voice) and none of them works sufficiently well.

Yes, the g.729 licenses can get expensive. We went the route of the Digium transcoder cards. Gets you a big bulk license.

Sounds good if you are handling a lot of call. I don’t know what Spitfire use to terminate their calls. I suspect it’s not Asterisk.