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The Model 408 is a 5-level liquid level sensor designed for use with bubbler-type systems. The 408 contains an internal air pressure transducer; the user must provide a small air compressor capable of supplying a maximum of 15 psi. This operates the system to a liquid depth of 34.6 feet. The output of the 408 connects to the inputs of the Model 407 3-Pump Liquid Level Controller (replacing the float switches) or to a Model 448 Output Relay Board. A 4-20mA signal output is provided as an input to process controllers or for other control applications. A 3-digit LED display continuously shows the liquid depth to 0.1 foot when the display control switch is in the Liquid Level position. Other switch positions allow setting of the corresponding trip level points. The trip points are set using coarse and fine adjustment pots, and are shown on the LED display. Each trip level has an LED indictor which illuminates as the solid-state output makes. A test feature allows the trip settings to be checked without actually changing the liquid level.