| 摘要 |
A vertically-oriented hydraulic cylinder has its piston rod attached to a pulpit or a lectern that is vertically guided as the piston is actuated. The hydraulic cylinder contains a column of oil in the cylinder between the piston and a supply line connected to the cylinder and coming from a water main such as a city domestic supply. An exhaust line off the supply line exhausts on the piston downstroke to a drain or sump. Each of the supply line and the exhaust line is controlled by a solenoid operating valve electrically connected to a manual switch. Preferably a limit switch located to be actuated at the bottom of the downward travel of the speaker's apparatus closes the exhaust valve before the oil-water interface in the cylinder reaches the cylinder outlet to the supply line. The supply entry of the cylinder may be baffled to reduce water turbulence to preserve the interface between water and oil in the cylinder.
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