| 摘要 |
Two sensors, which are connected to a controller, are arranged one above the other in the supply container of an electrical hot-water boiler for omnibuses. Said controller produces an output signal which influences a switching device which is connected between a voltage source and the heating wire of the boiler. If the water level in the supply container is lower than the upper sensor, the connection between the voltage source and the heating wire is interrupted by the switching device. At the same time, a warning device is used to tell the user that the supply container must be refilled with water in order to operate the boiler. The sensors are electrically conductive, elongated surfaces, while the controller is an electrical circuit.
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