Safety alert and locating system

Claim 2

A safety alert and locating system comprising, means for transmitting first and second coded interrogation signals from a central location, each of said first and second interrogation signals containing at least one address code, said first signal being transmitted through a first transmission medium and said second signal being transmitted through a second, different transmission medium, one or more individual means adapted to receive said coded signals, each of said individual means being located at a distance from and at an angle to said central location and being responsive to its own address code contained in said first and second signals, each of said individual means being adapted to transmit a response signal upon receipt of at least one of said first and second signals addressed to it, the response signal being transmitted through the transmission medium through which the signal was received, means at said central location for receiving the signal transmitted by said individual means, and location determining means at the central location for determining from the received signal the distance and angle of said individual means relative to said central location.

Claim 3

A safety alert and locating system as claimed in claim 1 wherein said means for transmitting comprises means for transmitting said first signal through air and means for transmitting said second signal through water.

Claim 4

A safety alert and locating system as claimed in claim 1 wherein said first and second coded interrogation signals are ultrasonic signals of different frequencies.

Claim 5

A safety alert and locating system as claimed in claim 1 wherein each of said individual means transmits an ultrasonic response signal through water when it receives an interrogation signal through water, and transmits a radio frequency signal through air when it receives an interrogation signal through air.

Claim 6

A safety alert and locating system as claimed in claim 1 wherein said first and second coded interrogation signals comprise pulse width modulated ultrasonic signals containing timing, address, and function segments.

Claim 7

A safety alert and locating system as claimed in claim 1 wherein each of said individual means transmits a single pulse response signal upon receipt of a coded interrogation signal addressed to it.

Claim 8

A safety alert and locating system comprising a base unit, a plurality of remote units located at an angle to said base unit, said base unit including means for transmitting first and second encoded interrogation signals through first and second transmission media respectively to individual ones of said remote units, said signals requiring a finite time to reach said remote units, each of said remote units being adapted to respond to interrogation signals addressed thereto to transmit a response signal through whatever transmission medium said remote unit is in, means associated with said base unit adapted to receive the response signals from said remote units, said means including first means for measuring the time that elapses from transmission of the interrogation signal to reception of the response signal and converting the time thus measured to a distance indication, said means associated with said base unit including a plurality of spaced signal receiving members each of which responds differently to the response signal depending upon the angle of incidence of the response signal upon said plurality of signal receiving members and means for measuring the differences between individual ones of said members as the response signal is received, and converting the differences to an azimuth indication.

Claim 9

A safety alert and locating system comprising a base unit, a plurality of remote units located at an angle to said base unit, said base unit including means for transmitting first and second encoded interrogation signals through first and second transmission media respectively to individual ones of said remote units, said signals requiring a finite time to reach said remote units, each of said remote units being adapted to respond to interrogation signals addressed thereto to transmit a response signal through whatever transmission medium said remote unit is in, means associated with said base unit adapted to receive the response signals from said remote units, said means including first means for measuring the time that elapses from transmission of the interrogation signal to reception of the response signal and converting the time thus measured to a distance indication, said means associated with said base unit including a plurality of spaced signal receiving members each of which responds differently to the response signal depending upon the angle of incidence of the response signal upon said plurality of signal receiving members and means for measuring the differences between individual ones of said members as the response signal is received, and converting the differences to an azimuth indication.

Claim 12

A method of monitoring the condition and location of one or more individual entitles as claimed in claim 8 wherein the response signals are received through the air.

Claim 13

A method of monitoring the condition and location of one or more individual entities as claimed in claim 8 wherein the response signals are received through water.

Claim 14

A method of monitoring the condition and location of one or more individual entities as claimed in claim 8 wherein the individual entities are addressed in sequence by the interrogation signals.