To make it possible to detect whether or not an appropriate battery is used and whether or not the battery is in a defectless state.

An emergency lamp turn-on device is provided with a charging transformer 3 which transforms the voltage of commercial power supply 1 and a rectifier 4 which rectifies the output of the transformer 3. The turn-on device is also provided with a battery 7 which is changed with the output of the rectifier 4 supplied to the battery 4 through a charging resistor 6 and a relay 2 for detecting power failure incorporating a normally-closed contact 32 which is opened when the power supply 1 is interrupted and a normally- opened contact 31 which is closed when the power supply 1 is interrupted. In addition, the turn-on device is also provided with a comparing and discriminating circuit which is composed mainly of a comparator 9 (including 1/2 and 2/2) which detects the charged voltage of the battery 7 when the battery 7 is changed and judges whether or not the voltage falls within a normal charged voltage range and a pilot lamp 20 which indicates abnormality when the charged voltage is out of the normal charged voltage range.