This circuit that generates a special sound was found in a Popular Electronics from the 90s. The base is the 555 and the transistors admit equivalents, and a power stage can be added.
With this luminous remote control, which we found in a 1990 publication, using a flashlight you...
We found this circuit in a 1967 Electronics World. The circuit can be designed to control other...
This circuit can be used in a signal level indicator with LEDs. The circuit is from an Electronics Now...