This is a read-write true/false setting controlling whether a frame CRC is included in the AMR-NB payload, applicable only when the peer uses octet-aligned RTP framing, and like the related AMR-NB objects it's only instantiated when the coder is AMR-NB. An admin enables this to add error-detection robustness to the AMR-NB payload at the cost of a small amount of additional overhead per frame. For example, an admin on a link with a history of bit errors might enable CRC on an AMR-NB peer to help detect corrupted frames.