Various diagram

Burglar Alarm Circuit

This is a very useful schema for you all.This is actually little bit different schema.Because this schema has used little bit advance knowledge.This schema operates with 9V.You can fix this schema for a door(SW1).Its ok though people use this door.But if some one keep opened it more than 30 seconds the alarm begins to ring.only users should know they should closed the door before 30 seconds.Think different way and use this in different way.