This circuit is intended for underwater communications. Of course, the critical point is the shielding to avoid water. The circuit is from an Electronic Hobbysts Handbook from the 90s.
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...