| 摘要 |
<p>The operation of the system is based on the electromagnetic radio-frequency link between the key ring and the proximity sensor, since the acoustic alarm is activated whenever the distance between the key ring and the proximity sensor exceeds a critical value (approximately 1 m), which is adjustable at the time of calibration. The invention can also be used as an all-purpose warning device for preventing loss of any non-metallic container, purse or bag into which the device to be attached to the key ring has been inserted.</p> |
