We found this precision circuit in a manual from the 80's. The operational amplifier is of a common type at the time, and equivalents can be tested. Transistors are general purpose types.
This circuit deactivates devices powered by the power grid so that when the power returns, they do...
We found this circuit in a 1998 publication. It drives an incandescent lamp for a time that...
This tachometer from a 1994 publication has a bargraph scale with the well-known LM3914 integrated...