Found in a radio amateur magazine of the 1980s, this circuit uses components that can still be found easily. The circuit is for NiCad batteries.
We found this circuit in an old American documentation from the 70s. The Triac can be of any type...
The quadrature oscillator is another type of phase shift oscillator, where each of the three...
This low frequency signal converter was found in the July 1983 issue of Radio Electronics...