A sensor encoder is a special device that was developed and used by Xindi-Reptilians. They are found somewhere aboard their ships and keeps sensor records. In the event a ship is destroyed, the encoder is ejected and floats in the debris field. If the crew's superiors receive no communications, an analysis team will be dispatched to find the encoder and find the cause of the ship's destruction.
An encoder from a Reptilian scout ship revealed that the ship was destroyed by Degra, giving Commander Dolim ample reason to murder him. (ENT: The Council)