This circuit was found in an Australian publication from 1991. It is a transmitter that transmits a signal when it detects moisture. The range is on the order of a few tens of meters.
This circuit is from an old documentation. However, it can be mounted with modern equivalent...
In the figure we have the way to add hysteresis to an operational amplifier. The relationship...
This video game is another of the AY3 series with the AY3-3606 integrated circuit. The circuit was found...