| 摘要 |
A rotating panel (10) is rotated by the speedometer needle and in a circuit for transmitting an alarm sound, a slot (11) is mounted for passing through light from an emitting diode (20). The emitting diode (20) lights up by the electric power source loaded from an alternator or batteries when the engine of automobile has started; a multivibrator (30) comprised of transistors (TR1-TR2), resistors (R1-R4), and capacitors (C1-C2) generates a square-wave pulse signal whose output-level is adjusted by capacitors (C1-C2) and resistors (R1-R2). A transistor (TR4) receives lights from the emitting diode through the slot of rotating panel and when being switched on, the transistor (TR4) loads the power source (VCC) onto the ground through the diode (D2). A transistor (TR3) is switched on depending upon a square-wave pulse signal which is loaded onto the base terminal from the multivibrator. An alarm generator transmits an alarm sound to the driver when TR3 and TR4 transistors are switched on.
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