Reference: https://downloads.avaya.com/css/P8/documents/101028405 Page: 21

When creating an Avaya IP Office™ solution spanning multiple sites, the Avaya IP Office™ Line (SCN) trunk type is used to interconnect the sites. The SCN (Small Community Network) trunk allows multiple IP Office systems to communicate with each other, enabling features like call routing between sites, shared directory access, and centralized voicemail.

The function to hear a secondary dial-tone when making outgoing calls is enabled through the Short Code configuration. Short codes in the Avaya IP Office™ system can be set up for various call handling features, including the option to play a secondary dial-tone during outbound calls.

Reference: http://www.tek-tips.com/viewthread.cfm?qid=1760220