Hall current monitor (CB7384E)

Found in an EDN from the 90's this circuit makes use of unusual components today.

| Clique na imagem para ampliar |

Open Fuse Indicator (CB6692E)
Found in old documentation about neon lamps, this circuit shows how to add a simple blown fuse...
Liquid Level Alarm (CB5310E)
This circuit was found in a 1980s documentation. It triggers a relay when liquid from a reservoir...
Cascading the 4520 (CB083E)
For counting to values higher than 16, many 4520 can be cascaded as shown in Figure . The EN...