Have to agree with Woderick - there's two types. Older units did the correction in the Altimeter but more modern EFIS-equipped aircraft input the correction from the Air Data Reference Panel (ARP in Rockwell-Collins) to the DADC. Both 29.92 and Baro-Corrected Altitude is output on the 429 buses. A feature of these systems is that one push on the center of the Bar Correction knob turns the Altitude over to 29.92.