This filter was found in an American publication from the 1980s. The circuit can be implemented with any operational amplifier. The power supply must be symmetrical.
This circuit with a double-gate MOS transistor was found in a Popular Electronics from the 90's....
This photoelectric cell light relay was found in Radio Electronics magazine from April 1958. The...
This circuit was obtained in the publication 101 Electronics Projects of 1979. The circuit can be...