This circuit was found in a 1991 PE Hobbyst Handbook. The components are still common and each note has an individual adjustment.
The very high-input impedance of the CMOS gate allows this kind of device to be used as a...
This is a commercial circuit from the year 1958. Transistors are germanium types and transformers...
This very low current circuit with the ICM7860 was found in the April 1995 Electronics Now...