I dont know what to do with this problem. Could someone please draw the diagram (with paint etc) and upload it and explain what is happening to me?

An intruder alarm in a home security system consists of a light beam and an alarm which is triggered if the light beam is broken, even if only briefly. Draw a combined circuit/logic diagram. The system uses an LDR (as in question 2 above) to detect the beam, with a sensitivity adjusting potentiometer and Darlington threshold detector. If the light beam is broken a resettable alarm is permanently triggered.

 

Hello,

You can draw the circuit yourself.
Take a look to this blog of Bill_Marsden on howto use paint as "paintCAD" :
http://forum.allaboutcircuits.com/blog.php?b=49

Bertus

 

The thing is that I dont understand this problem i.e. I cant draw it

 

This might be useful as a starting point.

http://www.electronickits.com/kit/complete/elec/ck1602.pdf

The same idea in your question is implemented .... but .....
You would have to simplify this circuit and also add a circuit function to latch the intruder detected condition and a reset function.