| 摘要 |
An alarm is disclosed herein for providing an indication when a certain condition, such as a door ajar condition of a refrigerator, has existed for a predetermined time. The alarm includes a capacitor, means coupled to the capacitor for charging same while the certain condition is in existence, an indicating device and a voltage sensitive switch coupled to the capacitor and to the indicating device for repetitively partially discharging the capacitor through the indicating device when the charge on the capacitor reaches a particular level. A series of alarm pulses are thereby developed by the indicating device once the certain condition has existed for the predetermined time whereby the alarm pulses are separated by equal intervals substantially shorter than the predetermined time. The alarm of the instant invention is simple in construction and inexpensive.
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