Patent ID: 6888454

Claim:
A fault diagnosis circuit for an LED indicating light, characterized by: an LED indicating unit ( 3 a , 3 b ); a pulse generating circuit ( 7 ); a current detecting circuit (R 1 , Q 1 ) for detecting a flowing current by flowing a pulse of a current through said LED indicating unit ( 3 a , 3 b ) based on pulses generated by said pulse generating circuit ( 7 ); a comparing circuit ( 8 , 22 ) for comparing a current value detected by said current detecting circuit (R 1 , Q 1 ) with a threshold value (E 1 ) to judge a disconnection; a remaining circuit ( 10 , 26 ) for generating a signal and retaining the signal when the current value is judged as being smaller than the threshold value (E 1 ) as a result of a comparison by said comparing circuit ( 8 , 22 ); and an output circuit ( 28 ) for outputting a disconnection notifying signal based on the signal retained by said retaining circuit ( 10 , 26 ); and wherein: a time width of the pulse of the current flown through said LED indicating unit ( 3 a , 3 b ) is set too short to perceive light emitted from said LED by sight.