We found this circuit in a 90's EDN. The circuit is based on a control integrated that is still common in these types of applications. The circuit uses a PROM.
This simple metronome, from 1985 documentation uses only transistors and has two settings. For...
We found this circuit in a 1988 documentation. The circuit uses a conventional complementary...
This circuit was found in a 1990 publication. The sensors are electrodes placed in the water tank...