Hi JK,
Quite easy, check the EX90 TC5.1 admin guide, this also works for the C60:
http://www.cisco.com/en/US/docs/telepresence/endpoint/ex-series/tc5/administration_guide/ex-series_administrator_guide_tc51.pdf
You can configure that on the tsh:
check:
"H323 Profile 1 Authentication" and "SIP Profile 1 Authentication" in the linked documentation if you need more info.
xconf SIP Profile 1 Authentication ?
*? xConfiguration SIP Profile [1..1] Authentication [1..1] LoginName: < 0="">>
*? xConfiguration SIP Profile [1..1] Authentication [1..1] Password: < 0="">>
xconf H323 Profile 1 Authentication ?
*? xConfiguration H323 Profile [1..1] Authentication LoginName: < 0="">>
*? xConfiguration H323 Profile [1..1] Authentication Password: < 0="">>
*? xConfiguration H323 Profile [1..1] Authentication Mode:
Regards the VCS, check the admin guide and the authentication guide might also be useful for you
as its also important to understand how the authentication itself on the VCS works:
http://www.cisco.com/en/US/docs/telepresence/infrastructure/vcs/admin_guide/Cisco_VCS_Administrator_Guide_X7-1.pdf
http://www.cisco.com/en/US/docs/telepresence/infrastructure/vcs/config_guide/Cisco_VCS_Authenticating_Devices_Deployment_Guide_X7-1.pdf
http://www.cisco.com/en/US/docs/telepresence/infrastructure/vcs/config_guide/Cisco_VCS_Basic_Configuration_Cisco_VCS_Control_with_Cisco_VCS_Expressway_Deployment_Guide_X7-1.pdf
In general http://tandberg.com/docs is a good starting point regards Cisco TP documentation
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