Thank for youur reply.

I have learned that when the M11X came out, the 451R receiver was not in the marked, and it came with the 451.

The M11X have two "modes", NORM and SHR. The NORM mode is the slowest and is compatible with analog servos and SHR was for digital servoes.

When the 451R came out the two speed modes was now SHR and the new ultra fast SSR. No more compatability with analog servoes.

But the display in the M11X can only display NORM or SHR. So when used with the 451R, NORM=SHR and SHR=SSR.

This is actually what is stated in a note on the Sanwa website on the product pages for the 451R and M11X.

Mystery (for me at least) solved :-)