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.
Found in a 1970's Radio Electronics, this circuit uses a triac to switch loads on the AC network. This...
This circuit uses a diode as a radiation sensor. The operational ones are old because the...
This 1969 circuit generates a high voltage that reaches 100 V from 16 V. The power is of the order...