| 摘要 |
A low-cost control system for irrigation valves and the like, including a station advance control unit and a plurality of valve control units connected in a series string by a pair of power supply lines from the station advance control unit, each of the valve control units being associated with a single valve or a single group of valves. When power is first applied to a valve control unit, it actuates the valve or valves with which it is associated, and blocks the flow of power to succeeding control units in the series string. When a station advance signal is transmitted along a third line connected to all of the valve control units, the most remote control unit to which power is connected responds by deactuating its valve or valves, and switching power through to the next unit in turn. The station advance control unit generates station advance signals to control a watering sequence, and automatically disconnects power from the valve control units upon the transmission of a further station advance control signal after the last valve or valves in the series string have been actuated.
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