PURPOSE: To prevent the erroneous operation caused by the noise due to an engine or wind, by stopping the issue of detection output in such a state that an engine runs at a high speed.
CONSTITUTION: A detection output control part 36 is constituted so as to select the driving or non-driving of an alarm 5 to detection output on the basis of the output of a number-of-revolution operating part 38. That is, the pulse like rotation signal corresponding to the number of rotations of the engine mounted on a vehicle is inputted to the operating part 38 from a number-of-revolution detecting means such as a tachogenerator detecting the number-of-revolution of the engine and counted by the operating part 38 to judge whether the engine runs at the predetermined number of revolution or more. When the number-of- revolution detected by the operating part 38 are a predetermined value or less, the control part 36 controls a detection output drive circuit 37 so as to drive an alarm 5 and prevents the driving of the alarm 5 even when there is detection output when said detected number-of-revolution exceed the predetermined value. Therefore, wrong information is not generated by the noise of the engine or the noise due to the wind impinging on a receiver 20.
INOUE HIRONOBU
KATAYAMA SUSUMU
AZUMA NAOYA
TAKAGI TOSHIMASA
