Patent ID: 7098799

Claim:
An alarm unit incorporated in an electric system to which a power voltage is supplied, the alarm unit comprising: a first voltage evaluation circuit, which determines whether or not the power voltage is lower than a first predetermined voltage and outputs a first accident state signal when the power voltage is lower than the first predetermined voltage, the first voltage evaluation circuit being operable only when the power voltage is higher than a second predetermined voltage, the first predetermined voltage being higher than the second predetermined voltage; a second voltage evaluation circuit, which determines whether or not the power voltage is equal to or lower than the second predetermined voltage, and outputs a second accident state signal when the power voltage is equal to or lower than the second predetermined voltage, the second voltage evaluation circuit being operable when the power voltage is between a third predetermined voltage and the second predetermined voltage, the second predetermined voltage being higher than the third predetermined voltage; and an output circuit, which outputs an alarm signal in response to either of the outputted first or second accident state signals.