Instructables

Step 8: Alternate construction and Theory

Instead of using a battery and solar resistor, you could just use a small solar panel. However, these are more expensive and tend to break more easily.

Theory: It may be possible to bounce the laser of glass behind which a conversation is occuring (such as a window) and pick up the sounds on the reciever, but I've yet to test it. Please let me know if anyone has tried this or has a better way to do this.
 
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bustedit6 years ago
Does altering the laser beam effect the output sound? Could I blow smoke across the beam or something, or would that be too much and just interrupt the signal altogether?
navaburo7 years ago
I have given this a try, and made an instructable about it!

http://www.instructables.com/id/Laser-Surveillance-System-for-under-%2420/

Enjoy!