ULTRASONIC PAGING DEVICE FOR UNDERWATER DIVERS

摘要

In devices used by underwater divers to summon other divers from a distance, an audible sound is transmitted through the water and must be heard by a diver's ear. In this invention, each diver carries an electronic device that transmits modulated ultrasonic acoustic waves through the water when he presses a pushbutton switch. This causes a similar device carried by another diver to emit an audible sound that the diver can easily hear. This device is effective over a greater distance because noise from breathing apparatus and the barrier of a diver's protective hood do not interfere with ultrasonic acoustic signals as they do with the detection of sound by a diver's ear. A number of different waveforms are used to modulate the acoustic carrier wave. These are used to convey information between divers, and to achieve separate operating channels so that independent groups of divers can use these devices in one area.