What is the difference between Standard and Custom AEC References ?

What is the difference between Standard and Custom AEC References ?

A Standard AEC Reference is used for applications in which the microphones are not being reinforced to the room they occupy. A Custom AEC Reference is used for applications in which the microphones are being reinforced locally. The Custom AEC Reference allows us to exclude the microphones reinforcement audio from the AEC Reference preventing "Self Referencing" which results in cancelation of the microphone audio to the far end. See the following Tech Note for setup and configuration of both Standard and Custom AEC References: https://www.clearone.com/sites/default/files/2019-05/CP2%20AEC%20Referencing.pdf