In the original publication of the 90s a 556 consisting of a double 555 is suggested. The circuit drives a speaker with good power. The power transistor shall be fitted with a heat sink.
In the figure we have the way of modulating or controlling the frequency of a relaxation...
This circuit monitors the current of a series of 40 V lithium battery packs connected in series....
This circuit is from an old Signetics documentation. It can be implemented with modern operational...