This circuit was obtained from Popular Electronics of the 1990s. The circuit uses common transistors today and the frequency is given by the crystal.
The 4518 can be cascaded to count to values higher than 10. The output EN of this device can be...
This instrument was obtained in a documentation for radio amateurs of 1976. The circuit measures...
We found this circuit in a 1966 US documentation. It simulates a variable capacitor that can vary...