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car alarm

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Roff

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I looked at http://www.electro-tech-online.com/threads/the-oscilloscope.56/. ElectroMaster, if you read this, you might want to comment, since I'm critiqueing your circuit.
I believe the base resistors are way too large. The LED is going to draw around 7ma. The buzzers that I could find specs on draw at least 5 or 6 ma. That's 12 ma collector current. The base current is about 38 ua. For the transistor to saturate, you will need beta to be over 300. This is not common in a garden-variety transistor, certainly not at low Vce, which is where the operating point is. I would make the base resistors no larger than 22k. 10k would be safer.
 
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