This circuit was originally recommended to give the call signal on intercoms. However, it can be used with other applications. The circuit is from 1978 documentation. The transistor may be the BC548.
LTC7841 PolyPhase® Synchronized Boost Controllers Mouser Announces Analog Devices LTC7841...
This is the basic version of a small audio oscillator with the LM3909. The circuit must be powered...
We found this circuit in a 1980s documentation. The circuit uses general purpose transistors,...