switch can be used during operation of the control system in a calibration mode during which a zero depth for the dipping unit 10 can be associated with the upper limit of travel for the dipping unit 10 if the control system is a microprocessor based intelligent control system feedback from the encoder 82 can be used to train the control system to slow the assent and descent of the dipping unit 10 to allow more gradual stops alternatively or in addition to the encoder 82 the current draw of the winch 72 can be monitored or the winch 72 cable 74 or pulley 76 can be equipped with a strain gage to sense when the dipping unit 10 encounters a body of oil at the lower end of the casing 62 and encounters the flange 56 at the lower fill and upper dump extents respectively of the dipping unit 10 as well as to detect any obstruction or other anomaly in the operation of the dipping unit 10 an intelligent control system is also capable of learning the optimum stopping point for effectively recovering oil on an ongoing basis for example through feedback from the encoder 82 strain gage and or water sensor 84 the control system can learn how deep to lower the dipping unit 10 how many cycles to complete before encountering water and how long an inactive period is necessary to allow oil from the surrounding substrata to replenish the oil well to a suitable level to permit reinitiating oil extraction in its manual operating mode the control system preferably enables an operator to press buttons to lower and raise the dipping unit 10 all.