| 摘要 |
PURPOSE: To automatically emit an alarm tone even at the time of an abnormal state like a theft by attaching an oscillation switch to a portable vessel. CONSTITUTION: When the distance between an alarm device 2 of the portable vessel and a person who carries a transmitter 1 provided with a transmission means is longer than a prescribed value, that is, when he is on the outside of the reception area, a timer circuit 26 is started by the operation of an oscillation switch 25 to set a reception circuit 21 to the operatable state through a transistor TR for a prescribed time. Since the reception level is low, the output of the reception circuit 21 acts on a reception sensitivity detection circuit 22 to turn on a dive circuit 23 and its control circuit. As the result, a sound generator 24 emits the alarm tone. Further, the voltage divided by a resistor acts on the TR, and the reception sensitivity detection circuit 22 is kept in the operating state even after the prescribed time set by the timer circuit 26 elapses. Consequently, the alarm tone is continuously emitted. |
