The document discusses the advanced features of the Bosch Communications Systems SIP interface called C-Soft. It provides an overview of the SIP call windows and controls for placing and managing SIP calls. Key features covered include call holding, forwarding, conferencing, transferring calls and using the contact list. The interface allows integration of radio systems with SIP calls and supports up to 5 users in a conference call. It also discusses licensing options using software keys instead of dongles.