Patent ID: 8022830

Claim:
A lifeguard alarm system for a swimming pool comprising: a sensing device configured for attachment to a user and to wirelessly transmit a warning signal; at least one electromagnetic wave receiver configured to receive the warning signal; and a host coupled to the at least one electromagnetic wave receiver and configured to generate an alarm in response to the warning signal; wherein the sensing device comprises: an acceleration sensor configured to measure speed of the user; a state sensor configured to measure an angular position of the user; a water sensor configured to detect whether the sensing device is in water and to calculate a submersion time therein; first, second and third detecting mechanisms for detecting a dangerous state from mutually different conditions selected from (i) an internal angle between the sensing device and a vertical line during a predetermined time period being greater than a predetermined angle, (ii) an accumulated horizontal distance during a predetermined time period being less than a predetermined value and (iii) an absolute accumulated angular change differing from a predetermined condition; a fail-safe mechanism configured to detect whether a submersion time of the sensing device exceeds a predetermined time period or the user has abnormal vital signs; and a microprocessor configured to repetitively: determine whether the dangerous state as detected by the first, second and third detecting mechanisms using mutually different conditions exceeds a predetermined time period; transmit the warning signal if the dangerous state exceeds the predetermined time period; utilize the fail-safe mechanism if the dangerous state does not exceed the predetermined time period; and transmit the warning signal if the fail-safe mechanism detects that the submersion time of the sensing device is excessive or the user has abnormal vital signs.