Found in a Popular Electronics from the 90s, it applies to the old answering machines that used tapes. It emits a warning beep on the drive.
This control for 1200 W of power was found in the documentation of General Electric of 1966 has a...
I found this circuit in an old English magazine from 1979, but it can be easily assembled with...
This circuit imitates the singing of a bird intermittently with the intermittency determined by C1...