This circuit was obtained in a documentation from the 70s. The operational amplifiers used are uncommon today. Modern equivalent types can be tried out.
The inverter circuit shown in the figure can be used to power a fluorescent lamp in an emergency...
This circuit was found in 80's Popular Electronics. The circuit uses an infrared-sensitive phototransistor...
Found in documentation from the 1980s, this circuit generates signals that can reach a few...