This circuit from Popular Electronics powers a small speaker. The transistor can be of general use and the capacitors can be altered to change the sound generated.
These simple weapon and target circuits with emitter and photoelectric sensor were found in a 1985...
We found this circuit in an old publication dealing with operational amplifiers. The circuit uses...
Suggested by General Electric in a 1967 documentation, this circuit replaces the Thryraton tubes used at...