Guidance system for underwater swimmers

Claim 1

A guidance system for underwater explorations comprising: transportable means for sensing an external magnetic field and developing a proportionate alternating voltage when the transportable means is so oriented that the magnetic field has a component along a predetermined null axis; said transportable means including compass elements azimuthally adjustable for setting a predetermined nUll axis to provide an initial heading; means connected to said sensing means for producing an electrical voltage representing proportional heading error, the amplitude of which is directly proportional to the magnitude of the field component present along the null axis; an audible tone generating means receiving the output from the proportional heading error voltage producing means, the pulse repetition frequency of the audible tone generator being varied in proportion to the amount of error voltage received; a pair of headphones worn by an underwater swimmer receiving the output from the audible tone generating means; gating means connected to the output of the audible tone generating means for directing the audible tone to the left earphone when the course deviation is to the left and to the right earphone when the course deviation is to the right whereby the underwater swimmer receives a signal indicating the magnitude and direction of any deviation from the initial heading; and a waterproof housing enclosing the transportable sensing means, the proportional heading error voltage producing means, the audible tone generator and the gating means; said waterproof housing including a base plate adapted for attachment to an underwater swimmer.