This circuit was found in a 1991 PE Hobbyst Handbook. The components are still common and each note has an individual adjustment.
Found in a Motorola's 1968 documentation, this circuit operates at 16.5 kHz. The output is 5 A....
Using an integrated circuit from the time, we found this configuration in a 90s Radio Electronics....
With a touch of the sensor, the output of the 4013 changes state from high to low or vice versa. In...