The Duress function requires connection to an alarm monitoring service.

Depending on the type of control panel in your system, you may have a 4-digit or 6-digit user code.

The Duress code is a sequence of 4 or 6 digits that covertly sends an alert to your monitoring service when it is entered instead of your personal User Code.

Enter this code if you are forced to disarm or arm the system under threat (for example, if someone surprises you and then watches you closely as you're entering the house).

When the Duress code is entered instead of a normal user code, your  security system's control panel appears to behave normally, but the system silently notifies your alarm monitoring service.
The Duress code is set at the system control panel by the System Administrator/Master User. It is set in the same way as regular User Codes.

See the FAQ titled How do I add, set up and delete Users? (User Management).