This sound intensity meter was found in a 90s Elektor. The circuit uses an integrated device from the time that is not common today. The indicator is a milliammeter.
This 10 mA microammeter circuit can measure currents of 50 uA. The circuit is from a publication from the...
This circuit charges a battery to power a flashlight at night. The circuit is from an English...
We found this transistor siren in an old English publication. The transistors are from the era,...