Using a 4046 PLL, which is not very common nowadays, this circuit was found in the October 1994 issue of Electronics Now magazine. The power is provided by the transistor and is small in this case.
We found this circuit in documentation from the 1970s; The circuit uses Japanese transistors of...
This circuit goes into operation producing a sound on a small speaker when the supply voltage...
Suggested by Harris in documentation from the 80s, this circuit uses components from that time. It...