yes, you are correct : the A4 receives speed via the CAN-bus, which can not be cut (or switched).. as a side note, the A6 receives speed via GALA wire, which can be switched..
the 1st option is the Dietz 1280.. this device "filters" out the speed signal from the CAN, but allows other signals to pass through such as "ignition turn on" and illunation.. when the 1280 is activated (via additional switch), you can not navigate..
in europe there are some companies offering to recode the RNS-E to allow video-in-motion, which does not disable navigation.. unfortunately there is some secret way to do this -- no one on this forum has figure out how to do it this way..
the 1st option is the Dietz 1280.. this device "filters" out the speed signal from the CAN, but allows other signals to pass through such as "ignition turn on" and illunation.. when the 1280 is activated (via additional switch), you can not navigate..
in europe there are some companies offering to recode the RNS-E to allow video-in-motion, which does not disable navigation.. unfortunately there is some secret way to do this -- no one on this forum has figure out how to do it this way..