Alarm systems generally will silence the siren if you disarm the system. It doesn't matter whether the alarm went off in the armed or disarmed state. Some alarm systems will allow you to disarm under duress---disarm the system and shut off the siren, yet still send a silent alarm to the central monitoring station.
Press the "off" or "unlock" button. This button sometimes has an open-padlock icon and can be colored green.
Enter your secret code. The system will disarm, and the siren will stop.
Alternately, disarm the system under duress. Enter the duress code, which was set by the installer. It works just like your secret code. The siren will stop, but a silent alarm is sent to the monitoring station.
Tips & Warnings
- If you are not there to stop the alarm, the siren will sound for the duration set by the installer. It then will stop for 30 seconds and repeat for the same time set by the installer. The cycles repeat to the maximum as programmed. The zone that triggered the alarm will be disabled for a period as programed, then enabled again. The default to re-enable is 24 hours after disabling, or sooner if you arm or disarm.