This circuit was found in an American publication from 1965. The circuit uses components from that time. No information was given about the excitation transformer. Observe the high input power.
This circuit is from a 1980s documentation, but the configuration can be applied to most modern...
This 0.5 Hz filter was found in the December 1990 issue of Radio Electronics magazine. The power...
This circuit was found in a 1977 Radio Shack documentation. The circuit is TTL, which must be...