Flood alarm (CB7994E)

This circuit is from a 90s Popular Electronics. The transistors are of general use and the buzzer is a Sonalert type.

Silicon Labs' Low-Power BGM113 Blue Gecko Module, Provides Short-Range Bluetooth Capabilities
October 17, 2016 - Mouser Electronics, Inc. is now offering the Blue Gecko BGM113 Bluetooth®...
Tesla Coil Without Semiconductors (CB22477E)
This is a basic version of the Tesla coil that does not use semiconductor devices, found in an old...
REF6000 Precision High Voltage Reference (COM094E)
September 2016 - It can be purchased at Mouser Electronics the new REF6000 precision voltage...