This circuit was found in a Popular Electronics of the 1980s. The microammeter may be the lowest current range of a multimeter. The antenna is telescopic.
This circuit is from Motorola's Linear Databook from 1990. The integrated circuit and transistors are...
This circuit was found in a 1995 documentation. It drives a set of sequential LEDs from the sound...
The integrated circuit used in this 90's circuit is not common today, but the configuration can be...