Communications – electrical: acoustic wave systems and devices – Underwater system – Analog speech communication
Patent
1994-12-09
1996-09-10
Lobo, Ian J.
Communications, electrical: acoustic wave systems and devices
Underwater system
Analog speech communication
367901, H04B 1100
Patent
active
055555330
ABSTRACT:
A control system which enables a diver to electronically switch between voice operated (VOX) operation and push-to-talk (PTT) operation by actuation of the existing momentary contact PTT switch used in most diver communication systems. A counter and multivibrator arrangement is employed to alternate between PTT and VOX modes in response to a pair of quick depressions of the PTT switch within a pre-determined time. An audio tone having a duration which identifies which mode of operation has been enabled is also generated and is available for input to the diver's earphone amplifier. The control system includes a frequency selective VOX enabling circuit which takes advantage of the repetition of vowel pitch pulses found in human speech. The circuit continually locks onto these pulses when they last for a few cycles but ignores noise (as found in diving masks) which has only random spikes without the periodic repetition of vowel frequencies in speech. The control system employs filtering and a low cost phase locked loop (PLL) integrated circuit to lock onto these periodic signals found in the diver's voice signature. A lock detection circuit provides a positive output signal which is used to enable transmission each time a valid series of vowel pitch pulses is detected. In a second embodiment, three quick depressions of the PTT switch within the predetermined time, allow the control of a third function, such as high frequency/low frequency operation, in addition to switching between PTT and VOX modes. An audio tone having a pitch which identifies whether high or low frequency mode of operation has been enabled is also generated and is available for input to the diver's earphone amplifier.
REFERENCES:
patent: 3789353 (1974-01-01), Hunter et al.
patent: 4096466 (1978-06-01), Johnson
patent: 4471492 (1984-09-01), Mann et al.
patent: 5136555 (1992-08-01), Gardos
Vermula et al., "A novel voice activated switch (VOX) for high noise environments", Proc. of the IEEE 1985 National Aerospace and Electronics Conference NAECON 1985, vol. 1, pp. 56-60.
Lobo Ian J.
Peck/Pelissier a California Partnership
Weber Jr. G. Donald
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