VOIP

Hardware

PSTN gateways

I tried out a Linksys SPA-400 with 3 PSTN analog phone lines and an Asterisk server running on a recycled PC. It probably works fine as intended, in an all Linksys system but I was never able to get it to work reliably with Asterisk. The irony is that the SPA-400 runs Linux and Asterisk internally.

You can download the source tarball from the Linksys site.

version 1.0.0.2

It's based on Monta Vista Hardhat Linux

• MIPS processor
• ?? Flash
• ?? RAM
• Linux 2.4 kernel
• Busybox
• Asterisk PBX software
• thttpd
• /usr/sbin/lightbox controls LED's
• dropbear ssh

After a few months of wrestling with it, we bought a TDM-400 and sold the SPA-400 on eBay.

Digium X100P

These are fine if you only need one line, cheap on ebay.

Digium TDM400

This is the card I am working with now. It's great.

Sipura SPA3000

I'd like to try one of these as a single line solution.

I have a SPA3102 now that I picked up for the Chintimini Wireless Project.

Software

Asterisk -- works well but pretty complicated for small installations. I have some set up notes here Asterisk.

FreeSwitch --

Kirk suggests a combination of

• pfSense (http://pfSense.com/) which is a FreeBSD based firewall project
• Freeswitch PBX (http://www.freeswitch.org/)

pfSense has a package management system and there is now a FreeSwitch package for it so this seems to warrant some investigation.

Asterisk

You might want to use an IDE/CF adapter that can hold two CF cards. This way you could stick in a smaller second card -say- 32 or 64MB and mount stuff like /etc/asterisk, /var/log, /var/run and voicemail etc on that one, possibly leaving the main card mounted read-only for most of the time.

http://www.limeylinux.org/

Using Digium cards for FXS/FXO

Zaptel modules

Use the command genzaptelconf -d to generate new config files. Generates /etc/zaptel.conf and /etc/asterisk/zapata-channels.conf files.

Echo cancellation and gain settings on FXO lines

This page covers both of these topics:http://www.asteriskdocs.org/modules/tinycontent/content/docbook/current/docs-html/x1695.html

This one is interesting too: http://www.rowetel.com/blog/?p=18

1. Edit /etc/zaptel.conf to adjust receive and xmit gain levels.
2. Use ztmonitor channel to see levels during a call.
3. Use asterisk -r and the reload command to change settings during a call.

Web interface

Voicemail

User interface

On delete of message, move it to Trash/

Administration interface

• Should trashed messages be deleted or archived? How often?
• Should messages marked as old be deleted or archived? How often?
• Per user control of Trash/ ?

Service providers

Internet Telephony Service Providers

Links

Asterisk

Digital signal processing and Spandsp: http://www.soft-switch.org/

The Blackfin project http://rowetel.com/ucasterisk/