Hi Andres,

Hope all is well with you :)There is nothing to configure in CCM to start using Headsets on a 7940. There are many compatable makes and models available, many require a special cord to connect to to Cisco phone models. We are a Plantronics shop here at our Campus, so I can only give you feedback on them. We have many of the 3 models listed below working perfectly with 7941's and 7961's and other 7940's and 7960's.

Corded - Plantronics H171 or H17N (N = noise cancelling) ** nice lightweight Headset with multiple user wear options.

Make sure that you also order the following part for any Plantronics corded models;

Part# Amp 26716-01

Cordless - Plantronics CS50,CS55,CS70 - Great coverage (up to 200-300 feet) multiple channels (CS50 - 900mhz CS55 - 1.9khz) 8 hour battery life.

http://www.plantronics.com/canada/en_US/products/cat29880043/cat29880043/prod5210004

Hope this helps! Wow, I sound like a Plantronics saleperson (but they are excellent) :)

Rob

PS: If you are having problems with a particular setup let me know and we will try to figure out the issue.