In use telephone indicator (CB8657E)

Found in a 90s Popular Electronics, this circuit keeps an LED on when a phone is in use. Can be used with extensions.

Electronic Machine Gun (CB17369E)
Touching the sensor with your fingers, this circuit produces a machine gun sound. The circuit must...
Hearing and Motion Sensor Platform
August 2017 - STMicroelectronics' BlueCoin development environment is available at Mouser...
Garage Warning (CB6041E)
We found this circuit in an old documentation. Its purpose is to turn on warning lights when the...