Personal Alarm - These handheld piezo screamers are also known as rape alarms. They are a very loud siren. HOME

This one is particularly loud even though it runs on only two AA batteries. It uses a push-pull transformer output. This unit was manufactured with the 10K resistor at pin 4 instead of pin 3 due to a PCB layout error:
Circuit Diagram aka Schematic reverse engineered from circuit board
The transformer is very small
Image description goes here

I do not gaurantee the accuracy or safety of any information herein.
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Do not experiment with or build any of the above circuits.