Monitoring a young child in a crowded public area can be a difficult job. The electronic tether addresses this problem. The electronic tether is a child monitoring device which measures the distance between the child and parent, setting off an alarm to alert the parent when the child has wondered too far away. Existing systems that attempt this distance measurement are based on estimating propagation loss. This has proven to be inaccurate due to interference, multipath, and varying component attenuations. Using more sophisticated correlation techniques, the dependency of the measurements upon signal strength has been eliminated. Measuring the correlation between two reference signals and the received signal delayed by the round-trip path delay, yields an accurate distance measurement.
 

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