This circuit operates from 20 Hz to over 20 kHz and is easily tunable. We found it in a 70s documentation. The circuit can be implemented with modern operational amplifiers.
This 5.1 MHz oscillator was found in a 1980s American documentation. The used operational...
A NOR gate can be improvised using one NAND gate of a 4011 as shown here. The diodes are...
Found in the September 1982 issue of Radio Electronics magazine, this circuit triggers a relay...