A tilt switch apparatus has an acceleration sensor or sensors, a temperature sensor, an auto-zero function or switch, a central processing unit (CPU), a memory, a communication port, a current source circuit, a current sink circuit, an alarm output, an input power connection, a power conditioning circuit, a housing, an optional visual tilt, zero, and power indicator. The CPU monitors the temperature sensor and applies correction factors to the acceleration sensor reading to adjust for predetermined variations due to changes in temperature. The tilt angle is determined using the temperature corrected reading of acceleration due to gravity. The alarm output is generated when the measured tilt angle relative to an established reference plane exceeds a programmed threshold angle for greater than a programmed amount of time. The alarm output is discontinued when the tilt angle is reduced below the threshold angle by a programmed hysteresis angle for greater than a programmed amount of time. Optional signal indicators may provide a notice signal when the tilt angle exceeds the programmed threshold angle or some predetermined fraction thereof. Additionally there may be multiple signal indicators, which may indicate which direction, pitch and/or roll, the apparatus is tilting. There may also be a signal indicator which provides notices when the power is applied and when the apparatus is aligned with the reference plane.