Home PBX

Back in this post I mentioned that I was going to teach myself Asterisk, as part of a project to build a home PBX system. I thought it would be useful to outline what I’m trying to achieve, and why, before I start posting progress reports that might make little sense otherwise.

So, at the moment I have a single PSTN line into the house, which in addition to providing my phone service, also carries my ADSL service. Inside the house I have a series of extensions to various rooms, on which we currently have two old-fashioned wired telephones. Voicemail is provided at the exchange by our service provider. This works OK as far as it goes, but with five of us in the house, contention over the use of the one phone line is becoming an issue. In addition, despite being on the UK telephone preference service “opt-out” list, we still seem to get a lot of annoying cold-callers, mostly dialing in from abroad where UK legislation cannot affect them.

So, in an ideal world, my plan would be to initially add 2 more lines to the house using VoIP technology to alleviate the contention. Both would have geographic numbers associated with our local PSTN exchange, to allow me to nominally declare one inbound VoIP line for the children to share, and one for me to use primarily for when I’m working at home. However, outbound calls would make use of any of the available lines based on availability and a least cost routing algorithm.

I’d also replace the two wired telephones with several DECT handsets. My intent would be that each handset would operate independently of the others, and the system would support multiple parallel active calls. In addition, I would want to be able to conference together multiple handsets and/or multiple lines as needed.

Voicemail would be provided internally by the system, with individual accounts for each user, with messages forwarded to the user by email if required.

The system would also need to do time-based routing of incoming calls, so that after a specific time at night, all calls would go straight to voicemail, unless they come from a known and authorised number.

International callers, and callers with no CLI would always get trapped by the system and passed to an IVR system that would allow the caller to identify themselves. If they identify themselves as an authorised number then they would be passed on to the phones/voicemail, otherwise the call would be automatically terminated.

To create such a system I figure I need something like the following:

  • My existing PSTN line
  • 2 x geographic numbered VoIP lines
  • Asterisk to handle the signalling, with a fairly complex configuration
  • 1 x Linksys SPA3102 linking the PSTN line to Asterisk, and providing a fallback wired PSTN phone on one of its FXS ports
  • A Polycom Kirk Wireless Server 300 to provide the interface between Asterisk and the DECT handsets
  • A PoE injector to power the KWS300
  • As many DECT handsets as eventually needed

However, the outlay on that is a little on the high side, and the learning curve very steep indeed before I’d get to a working phone system. So I propose to do this in two phases, and start with:

  • 1 x PSTN line
  • 2 x geographic numbered VoIP lines
  • 1 x Quint package Siemens Gigaset S685IP

The Siemens Gigaset can handle some of my requirements out of the box, allowing me to get a basic working system up and running. It can also be interfaced to Asterisk, allowing me to start experimenting with Asterisk, before adding the SPA3102 and optionally upgrading the S685IP base station with the Kirk Wireless Server, reusing the handsets from the S685IP package as needed.

Well, it’s the current plan anyway 🙂

5 thoughts on “Home PBX

    • When I last looked at this (at the back of last year) Tesco seemed to have a good offering in their “Anytime UK” package, which gave a geographic number and unlimited free local and national calls of up to 70 minutes in duration, for just under £3 a month.

      Early reviews of their service were absolutely appalling, possibly not helped by them not initially running a standard SIP service, but they do seem to have got better over the last couple of years – or at any rate, there is less evidence of complaints. For my needs, if their service works as expected, then it would suit me just about perfectly. Their website is a complete mess though, making it very difficult to understand what their current offerings really are. They do seem to have changed since I last looked though – the 70 minute limit on free calls appears to have been withdrawn. It’s on my todo list to call their customer support line and see if I can find someone technical to talk to before committing myself.

      After that, Vonage have a similar offering to Tesco but for £6 a month, Sipgate have an offering that works out about £6 a month for 1000 minutes to UK landlines, and Gradwell (who focus on business use) have various offerings that all involve monthly and per minute charges ie potentially a lot more expensive. However, they also offer SIP and IAX2 trunks, which is very interesting but complete overkill for me.

      In short, the Tesco/Vonage offerings are attractive because they’re simple to understand, unlimited, and cover everything that I’d need. Tesco being 1/2 the price of Vonage seals the deal for me, provided it works OK…

  1. Pingback: DECT phones arrive « Richard’s Blog

    • They’ve a good range of the higher-end Kirk equipment, but not the KWS300. Mind you, I’ve found that just the Siemens Gigaset DECT system and a couple of VoIP lines have resolved enough of my problems that I’ve not gone on to build the more complex solution. It’s “good enough”, while also being “simple enough” that my family can cope with it.
      I am still tinkering with Asterisk though, and may get around to doing something more complex one day – just because I can 🙂

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