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:
|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|
|Ports:||4 USB 2.0,
1 microphone in,
|4 USB 2.0,
1 microphone in,
|4 USB 1.1,
1 microphone in,
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.