This circuit was found in a 1965 General Electric documentation. SCRs and unijunction may be current equivalents. The circuit has period adjustment and symmetry.
Found in old documentation about neon lamps, this circuit shows how to add a simple blown fuse...
This circuit was found in a 1980s documentation. It triggers a relay when liquid from a reservoir...
For counting to values higher than 16, many 4520 can be cascaded as shown in Figure . The EN...