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The present document specifies the media plane control protocols and interactions with the media needed to support a
Mission Critical Push To Talk (MCPTT) system interworking with a Land Mobile Radio (LMR) system. This
interworking includes both the signalling and the media planes between the MCPTT system and the LMR system. The
function between the MCPTT system and the LMR system is referred to as an Interworking Function (IWF).
The IWF supports the basic group and other features as specified in TS 23.283