Why Asterisk instead of Avaya Nortel Shortel or Cisco?

[michaelper22]

You mention in the video that you can use digital phones like the Avaya 6400 series with a "special interface card." What are these cards called, who makes them, and where can they be found?

I used an Avaya 6408D+ at a previous job of mine, and loved it. Power in simplicity. I'd replace the cordless phones in my house with them in a heartbeat if they didn't need a super-expensive PBX.