From TANGO Interactive Training NPAC Training -- Dec 11 and 12 1997. byMarek Podgorny
TANGO_PLUGIN_CONF and TANGO_APP_CONF variables point to TANGO configuration file directory.
There are two files there:
plugin.conf file defines TANGO server to be used
applications.conf file defines paths to non-Java applications of TANGO system. Typically, this file is modified to point to BuenaVista, the audio/video conferencing package
NCS_PATH variable is used by BuenaVista to find its own media modules. Without this variable BV won't be able to start audio and video agents.