Cisco AS5800 Voice Feature Cards (VFC) are full-featured voice processing cards that support Voice Activity Detection (VAD), comfort noise generation, adaptive jitter buffering, programmable echo cancellation, programmable frame size, and Dual Tone Multiple Frequency (DTMF) detection and generation. High-complexity (HC) Cisco AS5800 Voice Feature Cards offer a wide range of VoIP codecs, with Group III real-time fax support, on any port at any time.This medium-complexity VFC supports only codecs that require 20 MIPS or less per session.