We found this circuit in the October 1991 issue of Radio Electronics magazine. The circuit uses common components and can still be assembled easily today.
This amplifier was found in a technical documentation from the 1970s. The circuit uses 2N2218...
The frequency of each note depends on R2, which must be replaced by a keyboard. The circuit is...
This circuit warns when the headlight bulb is on. We found it in a Popular Electronics from the...