Using various PSTN carriers


If I were to buy an off the shelf avaya 406 or similar, the companies selling it to me would route my calls through pstn carriers like opel, or gemini (I’ve not been able to find any info on these companies) Would I be able to do the same thing with Asterisk, I presume that the Avaya simply prefixes the outgoing number with a code specific to the carrier in question? Or have I got this mixed up?

Also, what carriers are available. BT are very expensive compared to prices I’ve seen from SIP gateways and those companies who are trying to sell us an Avaya.

I’m based in the UK, so looking for UK specific info.

Thank in advance,

Just to answer my own question - for the benefit of others.

When you order ISDN in the uk the default carrier can be selected at install time, calls can be routed via other carriers by prefixing the outgoing number witha 4digit short code.

i dont know much about uk pstn but i can answer this-

Asterisk can prepend a code to your outgoing calls. it can (if you set up the dialplan to do so) prepend different codes or no codes based on time of day, day of week, who is calling, what line you’re using, etc.

Asterisk can also accept precodes from your users, and either pass them through or strip them or replace them based on the above criteria. It can also use codes to decide which physical lines to use, or to switch between voip and normal lines.

all this is done in extensions.conf.

does that help?

I’m based in the UK and spec’d and got installed an Asterisk server and sip phones for a 30 user system. PSTN in and out, and Voip to the desktop over the lan. c. 5K voice calls in and out per month and several hunt groups. Works really well, and all those functions that avaya would charge you for to ‘unlock’ are included e.g. vmail, IVR, moh, call stats, huntgroups etc.

For me it was an easy decision the cost saving was phenominal when I was comparing apples with apples. about 9K including 4.5K of deskphones and headsets. ok so it’s a little more risky but if you get a properly spec’d box, configed in the right way then its as reliable as you need it to be (since our last upgrade we’ve had 150 days+ continuous service)

To answer your specific Q - there are two ways in the UK of forcing calls to go by PSTN carriers other than BT (assuming your using BT lines) - IDA which as Ironhelix says is done on dial codes which can be inserted into the dial plan by asterisk or any other PBX or CPS in which case you sign up for a deal with a provider and the routing codes are installed at the local exchange. As IDA over-rules CPS then you can CPS the majority of your traffic to carrier x but then set-up a routing code in asterisk to route calls to carrier y if the end-user dials out using say an ‘8’ prefix rather than a ‘9’ - which can be handy in the event of issues with carrier 8. Or you could set it to route calls to Madagascar (for example) via y as much cheaper than x

I also agree with IronH about stripping what users dial and forcing asterisk to dial what you want it to dial - for example blocking PRS calls, and forcing users to a given 118 provider who are cheaper than 118500 etc.

drop me a pm if you want more info.

Thanks both. Berttie. It sounds like you have a very similar setup to ourselves. 40 users PoE phones, * server with IDSN PRI card. Also have SIP backup. I implemented a custom hotdesk solution also.

As for the carrier selection, our ISDN provider has preferred carriers that I’m happy to use to the dialplan hard codes the relevant prefix to the number based on the dialled number…

WRT to callling via PSTN or SIP I have it set to be able dial 9 for PSTN and 8 for SIP.

Thanks again.