Hi Venkatesh,
SX10 will work on SIP protocol only, however if you have expressway then you can leverage the SIP-H.323 interworking to get the h323 call work.
Please see below links for more information.
https://supportforums.cisco.com/discussion/12212026/sx10-call-type-scenario
This is for SX10 from Partner site
Q. Can I dial by IP address, without any call control device?
A. Yes, if you don’t have any call control device at all (CUCM, VCS), you can use IP address dialing. However, Cisco does not recommend this, for several reasons. NAT and firewalls cannot be traversed, for example, and inter-company dialing is therefore not possible.
Regards,
Raaj
