Found in an Electronic Design from the 90's, this circuit indicates three voltage levels by activating the LED in 3 modes: off, flashing and on for high voltage.
The power supply shown in the figure provides voltages between 0 and approximately 15 volts, with...
Another triggered oscillator that we found in the November 1984 Radio Electronics magazine. The...
Found in a 1980s German publication, this circuit tests batteries by type. The circuit is based on a...