The security chain is lockable from the outside of your house. Slip the lock through the chain that is on the door close the pad lock and it will keep an honest person out of your house. My alarm system does not have a time delay and it sounds the alarm immediately. I have some snoopy people that like to come in the house when I'm not home. This little trick stops them from coming in and doing anything at all. I even make it hard for them to pick the lock by keeping the chain short and when the door opens you can barely put your key in to the lock. Also works on interior doors to keep people out of your radio shack or man cave.