You might of ran into this bug: https://bst.cloudapps.cisco.com/bugsearch/bug/CSCuo92911/?referring_site=bugquickviewredir
try factory restting it, follow these steps:
https://supportforums.cisco.com/video/12504861/factory-reset-dx70-endpoint
you can download here:
https://software.cisco.com/download/release.html?mdfid=286310330&flowid=80562&softwareid=280886992&release=1.9.17&relind=AVAILABLE&rellifecycle=&reltype=latest
and for instructions:
https://www.acano.com/publications/2013/08/A...
that is correct. I would recommend to configure your sx20 devices to use H323 in Direct mode if you want to use as stand alone. SIP would require a SIP registrar/ SIP proxy server like CUCM or VCS.
To use SX20 as standalone , make sure you have th...