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.
Found in a 1980s telecommunications documentation, the circuit presented acts as a product...
It can be obtained from Mouser Electronics new transceiver modules long range (LORA) Microchip...
Working with the previous circuits, this circuit resets after 1 second. The circuit is from Radio...