The echo canceller expansion modules are user-installable, plug-in modules. The expansion modules provide a hardware-based echo cancellation feature that simultaneously offloads the work of the DSPs on the Signal Processing Mini-Module (SPMM) on the motherboard. By offloading this processing, hardware-based echo cancellation results in more robust echo cancellation.The echo canceller expansion modules enable high performance hardware-based echo cancellation for up to 64 voice calls.Dedicated Echo Cancellation Module 64-Channel is available for voice-only support on the 1-port RJ-48 multiflex trunk T1/E1 (VWIC2-1MFT-T1/E1) and on the 2-port RJ-48 multiflex trunk T1/E1 (VWIC2-2MFT-T1/E1) interface cards on the Cisco 1751 router.