In this tutorial, we are going to learn about Best Tutorial on Counter-Intelligence.
CounterIntelligence- Sometimes it is not really desired; that a burglar triggers a loud alarm sounds. What good would it be, if nobody is present who can hear it? In some cases it is better if a “silent alarm” is activated. If for examples someone is searching your drawers while you are not at home, it might be useful if you get some information about this preach of your privacy.The following circuit comes in handy for such application.The alarm contact has to be positioned in a way, so that the alarm contact is closed for a short time if a drawer is opened. The set-up itself must be hidden.If the drawer is opened by an unauthorized person, the LED lights up and indicate the attempted espionage. Now an investigation can be started unhurriedly. Finally the undesired guest may identified.The push button can be used to reset the sile alarm. How does the circuit work?
The circuit is symmetric. If it is switched on, one of the transistors is conducting. Which one is subject to chance? If for example Q1 is conducting, then the base of Q2 is pulled to minus potential. Q2 is shut off and the Led is dark. If he alarm contact is closed, the base of Q1 is switched to minus potential and Q2 conducts. The LED lights up. Only if the reset button is pressed, the LED will go off and the circuit is ready again. Applications:
Besides its application as counter intelligence device, the circuit can also be used as to check if the cat is inside your house. For this purpose, the alarm contact ha to be attached to the cat flap. If the red LED is on then you know, that your cat went out.