CCX does not have an ASR engine built in. You'll need to buy and integrate a supported server. When you do, all Media steps will automatically become speech-enabled. For example, Menu will accept DTMF or simple grammer input. Explicit Confirmation will accept 1 and 2 DTMF or yes/no grammers. Etc. The step reference guide provides additional detail on which steps support ASR.
Disclaimer: This is a highly simplified answer. Grammer definition and proper configuration of the ASR server are not trivial. If you already have an MRCP integration setup and have a more specific question or point that you're stuck on, please reply with additional detail.
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