This circuit is from a 1964 Electronic Design. The sensor is an LDR and the transistors are general-purpose types. The circuit triggers when the light that falls on the sensor is cut off.
We found this anti-theft circuit in a 90's English publication. The circuit uses common components...
We found this circuit in an Electronic Design from the 80's. The generated tone can be changed as well...
This astable multivibrator, well known to all, was found in the Raytheon transistor application manual of...