Hi I am wondering whether the Cisco 7940 is compatible to Isabel if yes is there a way anyone can help in making it work for a pay it's urgent.
herman -> YES, they are compatible but the installation is diffrent than a n ormal SIP pone. Check this tutorial (spanish) and let me know how far you get.
http://www.2how2.com/2014/05/cisco-telefonos-ip-79xx-con-asterisk.HTML