This circuit is from a 90s Popular Electronics. It consists of a power source for bass amplifiers of common types at the time that used symmetrical power and separating filters.
With the circuit shown it is possible to measure very low resistances, of the order of fraction of ohm,...
We find this circuit in documentation from the 1980s. The triac and diac are of conventional types...
This circuit is from an American publication about old neon lamps. The circuit is leak proof and...