call-manager-fallback :-- Enables Cisco Unified SRST feature support and enters call-manager-fallback configuration mode.
max-conferences :-- To set the maximum number of simultaneous three-party conferences supported by the router, Gain is used (Optional) to Increases the sound volume of VoIP and public switched telephony network (PSTN) parties joining a conference call.
transfer-system full-consult:--To configure your Cisco Unified CME system to use H.450.2 transfers
ip source-address 10.10.10.1 port 2000:-- This enable the SRST router to receive messages from Cisco IP phones through the specified IP addresses and port. its IP address and port number for IP phone registration.
max-phone 50:-- maximum phone in SRST mode
max-dn 300 dual-lin preference 10:- maximum dn in SRST mode.