Communications: electrical – Selective – Intelligence comparison for controlling
Patent
1976-02-17
1977-08-02
Farley, Richard A.
Communications: electrical
Selective
Intelligence comparison for controlling
325 16, 325 22, 325 28, 325 45, H04B 1100
Patent
active
040399990
ABSTRACT:
Amplitude modulation systems for underwater communication have a number of disadvantages. For example, with a number of divers attempting to communicate simultaneously, intolerable cross-talk occurs. Variable tuning is necessary to overcome this problem. However, the invention disclosed herein uses angle modulation (phase or frequency modulation) which inherently has fewer noise problems and, because of the "capture effect" reduces any cross-talk problems. In an exemplary embodiment an audio transducer feeds a modulator to produce frequency modulated radio frequency signals which are fed to a balanced modulator together with a fixed frequency radio frequency signal from a local oscillator. The output of the balanced modulator comprises ultrasonic frequency signals which are frequency modulated in accordance with the audio signals. Also disclosed is a receiver for such ultrasonic frequency signals. By the use of integrated circuits, a combined ultrasonic transmitter and receiver may be provided in a compact unit adapted to be strapped on the head of a diver.
REFERENCES:
patent: 2576157 (1951-11-01), Tykulsky
patent: 3218607 (1965-11-01), Brock et al.
patent: 3334300 (1967-08-01), Pischke et al.
patent: 3345568 (1967-10-01), Errichiello et al.
patent: 3427579 (1969-02-01), Sebesta
patent: 3470473 (1969-09-01), Gilman et al.
Gazey et al., Electronic Engineering, vol. 36, No. 436, June 1964, pp. 364-368.
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