Don't know if this will help Ed, I used to know this stuff, to damn old to remember, but this is what I found on the internet. I know it's a private line circuit, but that's about it. The 36 indicates a LEC ID.
CSNA
For AT&T Network Connection accounts. Select either CSNA (domestic) or CSNR (domestic and international) to trigger unique call processing. CSNA or CSNR cannot be standalone Subscribed Services on a TSG; either SDN or Toll Free Megacom must also be ordered with the CSNA/CSNR Trunk Sub Group.
The information was found
here
