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.
Maxim MAX20056B 6 Channel High Brightness LED Controller Maxim Integrated makes available through...
We found this circuit in American documentation from the 1980s. Transistors can be of general use....
This circuit for car engine spot adjustment was found in an 80's Radio Electronics. The circuit...