This circuit with zener diodes was found in documentation from the 90s. The zener diodes determine the lighting point of the LEDs. The circuit is for 12 V automotive batteries.
This car alarm was obtained in a Signetics documentation from the 1980s. The circuit uses the 555...
The frequency of this circuit can be varied from zero. The circuit uses the CMOS 4046 and was...
This simple binary counter triggers two LEDs according to the number of pulses applied to the...