Abstract: In one embodiment, a relative location detection apparatus including a detection unit having a support board having a plurality of spaced reed switches mounted along a lengthwise axis of the support board. Each of the reed switches has a longitudinal axis oriented substantially perpendicular to the lengthwise axis of the support board. A high intensity magnet is coupled to the support board for movement relative to the support board and in a direction substantially parallel to the support board's lengthwise axis. The magnet has north and south poles that are oppositely positioned to one another and directed toward one another across a width of the support board and into periodic alignment with the longitudinal axes of the reed switches. The magnet has a magnetic force sufficiently focused so that the magnet actuates the reed switches individually thereby indicating the magnet's location.

Abstract: The present invention generally relates to a cost-effective photocell switching circuit which can be manufactured as a single, factory sealed unit suitable for use in Class I, Division 2 environments. In accordance with the present invention, the switching circuit can be wholly formed with electrical components (i.e., without movable parts such as electro-mechanical relays). Further, features of switching circuits designed in accordance with the present invention render the electrical components immune to noise such that the components can be combined in a single unit, explosion-proof housing, thus reducing overall switching circuit complexity and production costs.