The Siren Safety Lock is a powerful door alarm. Don't take chances when securing your entry doors. The Siren Safety Lock uses the same security found in many hotels that allows you to partially open a door to see and speak with visitors while preventing the door from opening further. For additional security an built in alarm will sound if an intruder attempts to open the door. The alarm can alert you to the attempted break in, scare off the attacker, and summon help.