Water level monitor
When combining water and electricity it is essential that the current flow be a.c., else electrolysis will eat one elecriode away. This circuit was devised to give an audible alarm when a water tank was approaching empty. A switch was then ehanged over, a pump turned on manually, and when the alarm sounded again the pump was switehed off and tbe swirch reset, again manually. Sure, it would have been an easy matter to automate the process, but tbat was not considered appropriate for the application.