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How To: Building an Embedded Asterisk PBX

Choosing Hardware

Astlinux is available in several versions, each of which targets a different hardware platform.

  • Soekris Net4801
  • PC Engines WRAP Series
  • Generic 586 class PC

I am familiar with the Soekris single board computer hardware, having previously used the excellent open source m0n0wall router on a Soekris Net4501 system. Thus, for this review, I chose the version compiled for the Soekris Net4801 single board computer. This SBC is based upon a National Semiconductor Geode SC1100 processor, which is essentially a 266 MHz 486 class processor. In addition, the Net4801 provides the following hardware features:

  • 256 MB SDRAM, soldered on board
  • 4 Mbit BIOS/BOOT Flash
  • CompactFlash Type I/II socket, 8 MByte Flash to 4 GByte Microdrive
  • UltraDMA/33 interface with 44 pin connector for 2.5″ Hard Drive
  • Three 10/100 Mbit Ethernet ports (RJ-45)
  • Two Serial ports (DB9 and 10-pin header)
  • USB 1.1 interface
  • Power LED, Activity LED, Error LED
  • Mini-PCI type III socket
  • PCI Slot, right angle, 3.3V signaling only

When ordered with a suitable case and power supply, the completed system costs around $260.

Figure 1: Soekris Net4801, CF card, USB key & power supply

The Net4801 card is very small, and even the switching power supply is tiny. While the Net4801 supports an IDE hard drive, for this project the system will boot from a CF card, so it will have literally no moving parts. Since the system is destined for my home office, the fact that it is dead silent is a significant benefit.

In my earlier Asterisk installation, I had been using a Digium TDM-400p card to provide two analog line interfaces (FXO ports) to bring my lines from the telephone company into the Asterisk server. However, the basic case offered by Soekris Engineering does not provide sufficient space to fit a PCI card such as the TDM-400p.

Soekris does provide cases that will hold the Net4801 and multi-port LAN cards. In fact, they even offer a bundle combining the Net4801 with a Sangoma T-1 card, a suitable case and power supply. But for my home office, a T-1 interface supporting 24 lines is overkill. For this new installation I have decided that instead of using the TDM-400p card, I will simply call forward the analog lines to a phone number that is provided over IP from an online service provider. This way, if ever I have trouble with Astlinux, I can defeat the call forwarding and answer the main line using a plain vanilla analog phone that I keep on hand for just such an emergency. Given this strategy, the TDM-400p card is not required, which means the smallest, most basic case is adequate for this installation.

This Post Has 8 Comments
  1. […] read around here. The single most popular article is the one I wrote back in January 2006 about Building An Embedded Asterisk Server Using Astlinux On a Soekris Net4801. I would have thought that would have less appeal since it was published elsewhere over two years […]

  2. It’s very interesting for me, do you have any practical use for your home Asterisk server? Why you aren’t using any hosted PBX?

    1. Oh, yes. Between our home lines and my home office needs we put the little Asterisk system to good use. However, this article was originally written in late 2005. Since then I have migrated to using a hosted IP-PBX for most things. I still have a small Asterisk system on-hand as a testbed.

      It may come more into service if ever I complete my home automation project. I’d like to be able to remotely turn things off/on/open/close by way of DTMF as well as other methods, like the LCDs on my Polycom phones.

  3. Hi after days of searching web i found your site really helpful i am from India can you suggest any low cost IVRS solution for our small business i find digium analog cards very expensive is there anyway for analog card IVRS solution please give me a solution

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