Abstract: A large number of irrigation system devices connected to a common two-wire cable can be powered and individually controlled from a central location by transmitting over the cable DC pulses of alternating polarity. Control information is conveyed by transmitting a command pulse train consisting of a series of pulses, separated by short no-power intervals, whose polarities indicate logic ones or zeros. Following a command pulse train, a selected watering station decoder acknowledges receipt of instructions by drawing current during a predetermined pulse of an alternating-polarity power pulse cycle, while a sensor decoder returns binary data by drawing current during one or the other of the alternating-polarity pulses of a series of power pulse cycles.

Abstract: Neutral particles, such as atoms and molecules, transported along a path having at least one curved region are selectively conveyed or filtered according to each particle's velocity by generating an inhomogeneous magnetic field across a cross-section of the path. The neutral particles may be transported through a physical tube or simply through the region defined by the magnetic field. The path may have more than one curved region and may additionally have one or more straight regions. The magnetic field may be generated for example by homogeneously or inhomogeneously magnetized permanent magnets or by current carrying elements. The magnetic elements may additionally be used in conjunction with at least one piece of a high permeability magnetic material for focussing or containing the magnetic field.