This circuit was found in documentation for radio amateurs of the 1980s. This is the so-called roger-beep, which is the beep that is transmitted when the talk-listen function is changed.
This simple transistorized radio was found in a Japanese magazine from 1960. The phone must be...
This circuit counts from 1 to 10 or 0 to 9 using as indicators common LEDs. The circuit can be...
Found on Popular Electronics from 1969, this circuit can be implemented with components that are...