The SMS1242 microprocessor supervisory circuit reduces the complexity and number of components required to monitor the supply voltage in +5V, +3V and +2.5V systems. The SMS1242 will significantly improve system reliability and accuracy when compared to implementing the same functions with discrete components. The SMS1242 provides reset output during power-up, power-down, and brown-out conditions. It has a 1.25V threshold input detector for power-fail warning, low battery detection, or monitoring a secondary power supply. The part also integrates a separate active low manual reset input.