At this time, the Garmin 400W/500W series WAAS units are approved for interface to the following EFIS systems:

Honeywell EFIS 40/50 with the SG 465 symbol generator with the following limitation: No vertical guidance is provided for GPS approaches.

Sandel SN3308 with the following limitation: GPS lateral and vertical guidance is provided using the analog interface.

Sandel SN3500 with the following limitation: Vertical guidance is provided for GPS approaches.

This is specified in the latest Garmin 400W series installation manual P/N 190-00356-02 Rev. C, dated April 2007.