The Dynatrol level switch indicator from Automation Products, Inc., Houston, Texas, U.S., senses high, intermediate or low point levels in feed blending, grain storage or pellet mills, working on materials ranging from light fluff to heavy grains and pellets. When the probe is uncovered, it vibrates and produces an output signal, relaying a message that the probe is uncovered or that a low level exists. A covered probe does not send an output signal, relaying a message that a high level exists. Installation is simple and the probe can tolerate considerable buildup and caking. Switches can last up to 25 to 30 years.