US3740488A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Inductive loop through-the-earth communication system
Assignee: Westinghouse Electric Corp
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Filing: 1971-01-13
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Granted: 1973-06-19
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Expires: 1991-01-13
Abstract
Abstract A transmitter having a long line antenna grounded at both ends transmits audio signals through the earth to one or more receivers in a mine. Each receiver has a simple audio amplifier coupled to a loop antenna which compensates for greater attentuation of the higher audio frequencies being transmitted.
Inventors
- 👤 R Linfield
- 👤 A Farstad
- 👤 J Allen
- 👤 L Ball
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 16:36
CPC Classifications
H; H04; H04B; H04B5/00; H04B5/20; H04B5/24; H04B5/26; H04B5/266
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
158 words
A communications system comprising: A. transmitter means for transmitting, through the earth, an audio signal of a band of frequencies within the audio range; B. receiver means for receiving said signal; C. said transmitter and receiver means being for spaced apart operation with at least one being for location within the earth; D. said receiver means including: i. an audio amplifier; ii. means for connecting said audio amplifier to a source of operating potential; iii. a loop antenna coupled to said audio amplifier; and iv. output transducer means for converting the output signal of said audio amplifier to an audible signal; E. said loop antenna having an increasing output voltage vs. frequency characteristic, for a given magnetic field, said characteristic being linear up to a self resonant frequency, after which said output voltage vs. frequency characteristic decreases; F. said loop antenna being of a design that said self resonant frequency is above said band of frequencies being transmitted.
Claim 2
Dependent Claim
158 words
A communications system comprising: A. transmitter means for transmitting, through the earth, an audio signal of a band of frequencies within the audio range; B. receiver means for receiving said signal; C. said transmitter and receiver means being for spaced apart operation with at least one being for location within the earth; D. said receiver means including: i. an audio amplifier; ii. means for connecting said audio amplifier to a source of operating potential; iii. a loop antenna coupled to said audio amplifier; and iv. output transducer means for converting the output signal of said audio amplifier to an audible signal; E. said loop antenna having an increasing output voltage vs. frequency characteristic, for a given magnetic field, said characteristic being linear up to a self resonant frequency, after which said output voltage vs. frequency characteristic decreases; F. said loop antenna being of a design that said self resonant frequency is above said band of frequencies being transmitted.
Claim 3
Dependent Claim
54 words
A system according to claim 1 wherein said transmitter means includes: A. an audio frequency power amplifier; B. means for supplying said amplifier with operating potential; C. input means for supplying an audio signal to be amplified; D. antenna means; and E. means for coupling the output of said amplifier to said antenna means.
Claim 4
Dependent Claim
30 words
A system according to claim 2 wherein: A. said antenna means is a long insulated wire; B. the ends of said long insulated wire being for connection to the earth.
Claim 5
Dependent Claim
16 words
A system according to claim 2 wherein: A. said antenna means is a relatively large loop.
Claim 6
Dependent Claim
40 words
A system according to claim 2 wherein: A. said coupling means includes a transformer having a primary and a secondary winding; and B. said antenna means includes a first and second long insulated wire sections connected to said secondary winding.
Claim 7
Dependent Claim
52 words
A system according to claim 2 wherein: A. said coupling means includes a transformer having a primary and a secondary winding; and B. said antenna means is a long insulated wire connected to one end of said secondary winding, the other end of said secondary winding being for connection to the earth.
Claim 8
Dependent Claim
50 words
A system according to claim 2 wherein said coupling means includes: A. a primary winding; B. a secondary winding; C. said secondary winding including multiple taps; and D. means for selectively connecting said antenna means to said multiple taps for matching a variety of different antenna impedances to said amplifier.
Claim 9
Dependent Claim
32 words
A system according to claim 1 wherein said transmitter means includes: A. a plurality of antennas; B. said antennas being arranged in a predetermined pattern in accordance with a desired area coverage.
Claim 10
Dependent Claim
24 words
A system according to claim 1 for mine use, which includes: A. a miner''s helmet; B. said receiver means being mounted on said helmet.
Claim 11
Dependent Claim
123 words
Receiver apparatus for receiving through the earth transmission of an audio signal of a band of frequencies within the audio range, comprising: A. an audio amplifier; B. means for connecting said audio amplifier to a source of operating potential; C. a loop antenna coupled to said audio amplifier; D. said loop antenna having an increasing output voltage vs. frequency characteristic, for a given magnetic field, said characteristic being linear up to a self resonant frequency, after which said output voltage vs. frequency characteristic decreases; E. said loop antenna being of a design that said self resonant frequency is above said band of frequencies being transmitted; and F. output transducer means for converting the output signal of said audio amplifier to an audible signal.
Claim 12
Dependent Claim
123 words
Receiver apparatus for receiving through the earth transmission of an audio signal of a band of frequencies within the audio range, comprising: A. an audio amplifier; B. means for connecting said audio amplifier to a source of operating potential; C. a loop antenna coupled to said audio amplifier; D. said loop antenna having an increasing output voltage vs. frequency characteristic, for a given magnetic field, said characteristic being linear up to a self resonant frequency, after which said output voltage vs. frequency characteristic decreases; E. said loop antenna being of a design that said self resonant frequency is above said band of frequencies being transmitted; and F. output transducer means for converting the output signal of said audio amplifier to an audible signal.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-06-18 | 1976-12-18 | 1977-06-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-06-18 | 1980-12-18 | 1981-06-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-06-18 | 1984-12-18 | 1985-06-19 | $7700.00 | Window Closed / Lapsed |