https://supportforums.cisco.com/docs/DOC-24097
You could use below command to test SRTS , this would block communication with CUCM and Gateway
ip route
show ccm-manager – enter this command and check MGCP Fallback
Switchback mode: Graceful
MGCP Fallback mode: Enabled/OFF
During SRST mode you could enter show ephone summary and check the registered srst phones
show call-manager-fallback all - to verify SRST settings and version details
Configuring Cisco Unified 8941 and 8945 SCCP IP Phones -
http://www.cisco.com/en/US/docs/voice_ip_comm/cusrst/admin/sccp_sip_srst/configuration/guide/srst_setting_up_using_sccp.html#wp1362302