Found in Popular Electronics from the 90's, this circuit uses 555 integrated and common transistors to generate two tones determined by push buttons S1 and S2.
We found this circuit in a 1987 documentation, but it can still be easily assembled. Its output must...
This circuit that emits siren sound can be used in a fire alarm. We found it in an old American...
Found elsewhere in this section, this circuit is from the April 1971 Radio Electronics magazine. Note...