Portable underwater communication unit

Claim 1

A PORTABLE COMMUNICATION UNIT ADAPTED TO BE UTILIZED UNDER WATER, COMPRISING A WATER-TIGHT CASING, SAID CASING CONTAINING THEREIN, FIRST TRANSDUCER MEANS LOCATED AT ONE END OF THE CASING FOR CONVERTING ULTRASONIC ACOUSTICAL ENERGY INTO ELECTRICAL ENERGY, A BATTERY, AMPLIFIER MEANS CONNECTED FROM SAID TRANSDUCER MEANS, A DETECTOR FOR PRODUCING AUDIO FREQUENCY SIGNALS COUPLED FROM SAID AMPLIFIER MEANS, AND AN AUDIO AMPLIFIER COULPED TO THE OUTPUT OF SAID DETECTOR, AND SPEAKER MEANS SEPARATE FROM SAID CASING AND CONNECTED FROM THE OUTPUT OF SAID AUDIO AMPLIFIRE, FOR CONVERTING THE AMPLIFIED AUDIO SIGNALS TO SOUND ENERGY, BIASING MEANS IN CIRCUIT RELATIONSHIP WITH SAID AUDIO AMPLIFIER, SECOND TRANSDUER MEANS MOUNTED TO SAID CASING, A NORMALLY DEENERGIZED POWER OSCILLATOR IN CIRCUIT RELATIONSHIP WITH SAID SECOND TRANSDUCER MEANS, MANUALLY OPERABLE SWITCH MEANS DISPOSED ON THE OUTER SURFACE OF SAID CASING AND PLACED IN CIRCUIT RELATIONSHIP WITH THE BIASING MEANS OF SAID AUDIO AMPLIFIER AND WITH SAID POWER OSCILLATOR, THE ARRANGEMENT BEING SUCH THAT OPERATION OF SAID SWITCH MEANS SIMULTANEOUSLY ENERGIZES SAID POWER OSCILLATOR AND INCREASES THE GAIN OF SAID AUDIO AMPLIFIER BY VARYING THE NATURE OF SAID BIASING MEANS.