The 899 comes stock with the XHS 9 SI 180 T compact SI xducer that operates at 83kHz/200kHz 2d and 455kHz SI...

The 899 can use the XHS 9 HDSI 180 T xducer which operates at 83kHz/200kHz 2d and 455kHz/800kHz SI...

There were some early reports of issues with the 800kHz frequency when using the XHS 9 HDSI 180 T at 800kHz SI on the 899...

I think this may have been fixed in some of the latest software versions...

Rickie