A movement sensing means carried by a float in the pool is responsive to the movement of the float caused by the waves produced by the falling of an unauthorized object or person into the pool to actuate a wireless transmitter to send a signal to a receiver positioned at a remote location. The receiver, upon receiving the signal, actuates an alarm sounding means which provides a warning signal of the entry of the unauthorized person or object into the pool.

An alarm system is provided for detecting a seismic tremor and for generating an audio and/or visual alarm signal which varies depending upon the magnitude of the seismic tremor. In the preferred form of the invention, the alarm system comprises a free running oscillator having a pair of terminals the capacitive value across which controls the frequency of the oscillator. A fixed oscillator plate is electrically connected to one terminal while a variable position oscillator plate is electrically connected to the other terminal and has an inertial mass secured to it. A spring positioned between the plates urges the variable position capacitor plate away from the fixed plate but still enables the variable position capacitor plate to move in response to a seismic tremor thus varying the capacitive value between the terminals and the frequency of the oscillator. The output from the oscillator is coupled through a phase locked loop circuit which tracks the oscillator output. The output from the phase loop lock circuit is fed to a signal conditioner which shapes the amplitude response and in addition provides continuous recalibration to a zero output level when the device is unperturbed. The output from the signal conditioner in turn is coupled to an event classifier which compares the output signal from the signal conditioner with at least two preset reference levels. When the signal from the signal conditioner exceeds a first preset reference level, the event classifier activates a first alarm signal. When the output signal from the signal conditioner exceeds a second preset reference signal, the event classifier activates a second alarm signal.

A pool alarm includes a float body, a hollow container received in the hollow body; and tilt sensing mechanism in the hollow container to be placed in alarm mode when a water wave tilts the body.

An impact sensing device (16) is attached to a sporting implement to provide a visual indication of when the implement strikes a sporting object. The device (16) comprises a cylinder (22) containing a flexible wire (40) encircled by contacts (50 and 51). Upon impact between the sporting implement and the sporting object, the wire (40) flexes and oscillates to connect with the contacts (50 and 51). A circuit is closed and an indicator (18) is initiated by a power source (34). The sensitivity of the device (16) may be adjusted with first and second adjustments (24 and 26) to change the relationship between the wire (40) and the contact (50).

A floating digital display thermometer for a hot tub, spa or swimming pool, having a motion-sensitive switch responsive to wave action or intentional manipulation. The components are arranged within a watertight housing to ensure that a digital display always remains up to ensure easy viewing. Circuitry is provided for converting temperature readings to a digital display, and for indicating other functions such as time and date, and for providing alarm and music capabilities. Manually-activated membrane switches may be provided to activate various functions of the device. Furthermore, the thermometer is also capable of measuring and displaying the PH and the oxidation reduction potential of the liquid in the spa or swimming pool.