Is the 6150 fixed English keypad compatible with the SEM-Honeywell/ADEMCO Vista?

Yes. The 6150 fixed English keypad is a non-alpha keypad, so it only displays the numbers or sections/zones when programming. 

When a Uploader/Downloader (UL/DL) compatible SEM (SEM 210+)  is zone scanning, the keypad displays CC instead of MODEM COMM. When a legacy SEM (SEM 100 and SEM 200) is zone scanning, a zone scan appears to count upwards when scanning through each area.

For information about how some keypad errors display on a 6150, see SEM-Honeywell/ADEMCO Vista keypad errors.