The LM809/810 microprocessor supervisory circuits can be used to monitor the power supplies in microprocessor and digital systems. They provide a reset to the microprocessor during power-up, power-down and brown-out conditions. The function of the LM809/810 is to monitor the VCC supply voltage, and assert a reset signal whenever this voltage declines below the factory-programmed reset threshold. The reset signal remains asserted for 240ms after VCC rises above the threshold. The LM809 has an active-low RESET output, while the LM810 has an active-high RESET output.