Why is my 5800PIR-RES showing a Red flashing light?

The Honeywell 5800PIR-RES' Red LED blinks once per second while it is in power up mode. After initial power up, the 5800PIR-RES enters into walk-test mode. This mode will light the red LED for 3 seconds whenever the 5800PIR-RES detects motion. This mode lasts for 10 minutes upon initial power up. To restart the walk test mode, remove the batteries, then re-install them. See the following video for an example of how walk test mode is used.

The Red LED will never light up during normal mode.