| 摘要 |
An out-of-range monitor and alarm system that may be used by a convalescent home or the like to alert an attendant in the home that a supervised person has walked beyond a predetermined prescribed distance. The system includes a base unit that transmits a signal at a frequency F1 to a receiver in a mobile unit carried by the supervised person. The receiver includes a threshold circuit that is adjustable to correspond to the prescribed distance and produces a threshold output signal whenever the F1 signal detected by the receiver drops below the threshold level. In response to the threshold output signal, a transmitter in the mobile unit produces an F2 output signal to a receiver in the base unit, which in turn sounds an alarm indicating that the mobile unit has lost adequate F1 signal strength, as determined by the threshold adjustment, by exceeding the range prescribed for the supervised person.
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