The DSC LCD5501Z is a high-quality in-home smoke alarm. If your smoke alarm is going off, it has detected a problem. After investigating the area for smoke or flames, you'll want to reset the alarm and keypad. This shuts the alarm off and stops the beeping. It also brings the DSC back to its normal operating mode.
Grasp the outer edges of the keypad cover. Pull the cover down to access the DSC LCD5501Z's keypad.
Press the following keys sequentially: "Star," "7" and "2." This should reset the alarm.
Press the "Reset" button if entering the code does not work. The "Reset" button is located next to the "9" key.