capacitance type liquid level sensing switch the sensor 32 may be of a capacitance type also manufactured by the above mentioned company under the trademark capoint and as a model 520 2 the sensor 32 is operable to sense the presence of liquid oil at the level of a sensor probe 33 and to detect the absence of any liquid at that level the sensor 32 is operable in such a way that two signals are provided which are suitable for processing by a control circuit generally designated by the numeral 40 the absence of liquid at the level of probe 33 will provide a signal from sensor 32 to the circuit 40 and the presence of oil at the probe 33 will also provide a signal to the circuit the control circuit 40 is operable to receive input signals from the sensors 28 30 and 32 as indicated the circuit 40 includes flip flop circuits 42 and 44 an and gate 46 an or gate 48 a switch 50 and a relay 52 operably connected to the motor operator 54 of the valve 22 in such a way as to effect opening and closing of the valve in the schematic of the circuit 40 the connections between the sensors 28 30 32 and the circuit 40 are simplified in the interest of clarity and conciseness by for example eliminating reference to a source of electrical signal to be imposed on the sensors 28 30 and 32 for transmission to the circuit 40 a typical operating cycle of the system 9 may be carried out as follows assume the interior space 18 of the vessel.