D.I.Y. Asterisk Appliances: A Question Of Scale

5. Thin Clients

Now where getting into an area where I have direct, personal experience. Thin clients can make an excellent platform for running small Asterisk installations.

In most respects a thin client is simply a small, resource constrained PC. Their intended purpose is to give an end user a low-cost platform from which to connect to hosted resources on larger server systems. As they are usually not running a major application they don’t need massive amounts of memory or storage. They mostly provide the GUI layer for the end-user.

I was fortunate in that a few years ago someone gifted me a box of HP T5700 thin client from a scheduling system that was being decommissioned. The T5700 are older models and no longer sold, but there are newer and more capable models available currently. Here are some sample specifications:

Model: T5545 T5735 T5700
OS: HP ThinPro Debian Linux (2.6 kernel)) Win XPe
Processor VIA Eden Processor 1.0 GHz AMD Sempron 2100+, 1 GHz Transmeta Crusoe TM5800 733 MHz – 1.0 GHz
Memory: 512 MB DDR2 1 GB DDR2 256 MB DDR266
Flash memory: 512 MB 1 GB 256 MB
Graphics: VIA Chrome9 HC3 DX9 ATI Radeon X1250 graphics ATI Rage XC with 8 MB SDRAM
Network: 10/100/1000 10/100/1000 10/100
Ports: 4 USB 2.0,
1 DVI-D,
1 headphone,
1 microphone in,
1 serial,
1 parallel,
1 RJ-45,
1 VGA,
2 PS/2
4 USB 2.0,
1 headphone,
1 microphone in,
1 serial,
1 parallel,
1 RJ-45,
1 VGA
4 USB 1.1,
1 headphone,
1 microphone in,
1 serial,
1 parallel,
1 RJ-45,
1 VGA

The thin clients that I have seen come with auto-sensing universal power supplies and typically draw about 10 watts under full load. They boot from internal flash memory that’s on an IDE interface. The operating memory is usually one common SODIMM module.

For the earlier T5700 models HP offered an optional expansion package that’s intended to give the thin clients some expandability. The expansion package is a replacement for one side of the case and a PCI riser card. When installed it allows the thin client to accept one PCI expansion card.

I have used the expansion option in several ways;

  • To add a second network interface allowing me to use a T5700 as a router
  • To add a USB 2.0 card enabling the use of USB storage over faster USB 2.0 ports
  • To add internal space allowing the addition of a 2.5″ ID hard drive.

Thin clients are a bit on the pricey side when purchased new, however they are usually available much cheaper on E-bay. It’s not uncommon to see the T5700 series being offered in the $50-100 range.

If you want to buy them directly from HP you can often get a bargain by purchasing through the HP SMB Outlet, where I routinely see newer models in the $140-200 range.

Since you will be replacing the OS with your favorite Linux variant be mindful that you don’t need to pay extra for the models that include Windows CE or XPe licenses. The SMB Outlet often has models on offer without an OS, which is usually a little cheaper.

There is  one thing to bear in mind about older model thin clients; there may be some BIOS limitations. For example, my T5700s will only accept up to 512 MB of memory.

Because these thin client platforms are all based upon x86 processors you can treat them like a small server. Within the limits of the available CPU and memory they will run Digium’s G.729 codec or the Skype-For-Asterisk modules. My own experience is that a T5700 with 1 GHz CPU and 512 MB memory will easily handle four simultaneous G.729 transcodes, and was then limited by the number of G.729 licenses I owned at the time.

Given that a typical thin client doesn’t have a hard drive I tend to use them with Asterisk distributions that are built for use in diskless devices, like Astlinux or Askozia PBX.

6 thoughts on “D.I.Y. Asterisk Appliances: A Question Of Scale”

    1. boerner,

      I’m aware of these devices. However, at the start I made the conscious decision not include commercially available Asterisk appliances. There are many such devices available. I wanted to keep a decidedly D.I.Y. approach in mind. Further, I suspect that all of the commercial offerings are more costly than the platforms I wished to consider.

      I must admit that part of the appeal of the thin clients is that I was recycling hardware that was headed to the dumpster. It was at least a little green-ish.

      I do agree that David Rowe‘s work is awesome. We even had Steven Song from the Shuttleworth Foundation / Village Telco as a guest on a VUC call late last year.

  1. Another plug for the IP0X series, especially the very low cost IP01s & IP02s.
    They are so cheap that they are a good choice for the hobbyist / home enthusiast that wants to try out Asterisk.
    Here in New Zealand, we pay less than NZ$300 for an IP01.
    One nice thing about them is they include everything you need.

    On a related note, I once tried getting Asterisk working on a Linksys SLUG (the NSLU2) It was a royal pain. http://en.wikipedia.org/wiki/NSLU2

    I love the idea of an appliance to run Asterisk – no hard drive and no PC power supply to fail. And no noise and very low power consumption.

    My challenge is that I really like “HD Voice” (G.722) so want to run Asterisk 1.6 on an appliance – that has enough grunt to trasnscode G.722 to G.711 etc. Only need to support 3 or 4 concurrent calls at max though.

    1. Andrew,

      Almost all of the platforms that I described will run Asterisk v1.6 and support the use of G.722. Certainly the last three types described (thin clients, SBCs and net-tops) all have more than enough power to handle such matters.

      I know that the latest release of Astlinux uses Asterisk v1.6 and runs happily on the Fit-PC or and older Soekris Net4801. I’ve done both myself.

  2. Excellent read, I just passed this onto a colleague who was doing a little research on that. And he really bought me lunch simply because I discovered it for him smile So let me rephrase that: Thanks for lunch!

  3. Hey Michael,
    Excellent writeup. As I said, your site’s almost as addictive as Wikipedia. A note on REVO 3610.. I am using it as a media center, running regular Ubuntu Lucid with XBMC, playing Hi-Def content with barely getting into 20% CPU usage (720p). It’s a very powerful platform, that runs very little juice. For a proper office setup, you can easily use the Sangoma USBfxo unit, which (according to a quick ebay check) runs for about $125. The manufacturer offers driver source code for download. I haven’t tried working with it yet, but it’s a very interesting option for a hybrid setup.

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