Device for signalling spatial separation or closeness beyond or within a predetermined limit
OwnerPierre Sorriauxinventor
Life of this patent
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Abstract
A first unit (10) comprises a first transmitter (12) for wireless transmission of a signal in the from of periodic frames comprising identity information encoded in varying form in each frame, and a second unit (20) comprises a first receiver (22) for receiving said signal and for causing an alarm (29) to operate in response to failure to receive or to recognize identity information. Means (16, 26, 15a, 25a, 15b, 25b) are provided for automatically deactivating at least one of the first and second units when they are physically close together, and for automatically activating said units when they are physically separate from each other.
Claims21
Apparatus for raising an alarm when a separation distance between a monitored first unit and an alarm second unit exceeds a threshold, in which apparatus:
- the first unit includes means for wireless transmission of a signal containing identity information;
- the second unit includes means for receiving said signal and for causing alarm means to operate when the level of the received signal is below a predetermined threshold or when the identity information is not recognized in the received signal;
- and means are provided to cause the first unit and the second unit automatically to take up an inactive state and an active state respectively when they are physically connected to each other and when they are physically separate from each other, the apparatus being characterized in that:
- the first unit is a self-contained unit which includes encoding means for controlling the transmission of a signal in the form of periodic frames containing identity information encoded in a form that varies with each frame;
- and
- the second unit is a self-contained unit which includes decoding means suitable for recognizing the identity information in each received frame to cause the alarm means to operate over a predetermined time interval in response to failure to receive or to recognize the identity information in a frame or in a predetermined number of consecutive frames.
Apparatus for raising an alarm when a separation distance between a monitored first unit and an alarm second unit exceeds a threshold, in which apparatus:
- the first unit includes means for wireless transmission of a signal containing identity information;
- and the second unit includes means for receiving said signal and for causing alarm means to operate when the level of the received signal is below a predetermined threshold or when the identity information is not recognized in the received signal;
- the apparatus being characterized in that:
- the first unit is a self-contained unit which includes encoding means for controlling the transmission of a signal in the form of periodic frames containing identity information encoded in a form that varies with each frame;
- and
- the second unit is a self-contained unit which includes decoding means suitable for recognizing the identity information in each received frame to cause the alarm means to operate over a predetermined time interval in response to failure to receive or to recognize the identity information in a frame or in a predetermined number of consecutive frames.
Dependencies are inferred from the claim text.