摘要 |
A self checking system is disclosed in various forms, and is specifically shown as applied to a system which checks the level of water in a boiler before an associated fuel burner system is initiated. Before the liquid or water in the system can be processed, the liquid level is either caused to be depressed or is simulated as depressed, and this depression in the liquid level is sensed and the level verified before a circuit is completed in the liquid processing system. |