Krell Industries KRC-3 Owner's Reference Manual page 8

OPTIONAL CONFIGURATIONS
To enable these options, it is necessary to remove the top cover of the KRC-3.
1. Unplug the KRC-3 from the AC outlet.
2. Remove the KRC-3 top cover screws with the supplied T-10 Torx wrench.
Lift the cover from the KRC-3.
3. Find the two switches located toward the front of the board that are labeled
S3/proc and S4/tape. Set the dip switches to the position appropriate for
your application.
4, Place the top cover back on the KRC-3 and insert the cover screws.
5. Plug the KRC-3 back into the AC outlet.
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