US3895322A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Tone controlled compandored system
Assignee: AG Communication Systems Corp
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Filing: 1974-03-14
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Granted: 1975-07-15
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Expires: 1994-03-14
Abstract
Abstract A fixed power level frequency pilot tone, typically 4000 Hz, is inserted into the transmission baseband closely associated with each voice channel of a multichannel telephone cable system. The fixed-frequency pilot tone is a control signal that is transmitted through a voice transmitter compressor of a compandor system, together with the voice signal, and the pilot control signal is utilized at the voice receiver end to correctly expand the voice signal back to the required signal power level. The doubling of a transmission error of a conventional 2:1 compandor system is substantially reduced, being typically held to a few tenths of a dB.
Inventors
- 👤 James A Stewart
- 👤 Neale A Zellmer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 13:41
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/62; H04B1/64; H03; H03G; H03G7/00; H03G7/008; H03G7/06
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
188 words
In a telephone transmission system for communicating voice signals having frequencies within a passband that is more narrow than the bandwidth of an associated voice channel and having a transmitting terminal and a receiving terminal interconnected by a transmission medium, the combination: wherein the transmitting terminal comprises means responsive to the voice signals for generating a direct current control signal; means for generating a pilot tone of a fixed power level at a predetermined audio frequency outside the voice signal passband and within the channel bandwidth; means responsive to the direct current control signal for simultaneously compressing the volume range of the voice signals and adjusting the level of the pilot tone such that the relative output levels thereof are the same as the relative input levels thereto; and means for combining the compressed voice sIgnals and adjusted pilot tone and applying the combined output to the transmission medium; and wherein the receiving terminal comprises means responsive to the adjusted pilot tone in a received signal for compensating for losses caused by the transmission medium while expanding the compressed voice signals so transmitted to a predetermined volume range.
Claim 2
Dependent Claim
188 words
In a telephone transmission system for communicating voice signals having frequencies within a passband that is more narrow than the bandwidth of an associated voice channel and having a transmitting terminal and a receiving terminal interconnected by a transmission medium, the combination: wherein the transmitting terminal comprises means responsive to the voice signals for generating a direct current control signal; means for generating a pilot tone of a fixed power level at a predetermined audio frequency outside the voice signal passband and within the channel bandwidth; means responsive to the direct current control signal for simultaneously compressing the volume range of the voice signals and adjusting the level of the pilot tone such that the relative output levels thereof are the same as the relative input levels thereto; and means for combining the compressed voice sIgnals and adjusted pilot tone and applying the combined output to the transmission medium; and wherein the receiving terminal comprises means responsive to the adjusted pilot tone in a received signal for compensating for losses caused by the transmission medium while expanding the compressed voice signals so transmitted to a predetermined volume range.
Claim 3
Dependent Claim
25 words
The combination according to claim 1 wherein said generating means is responsive to compressed voice signals from said compressing means for producing said control signal.
Claim 4
Dependent Claim
63 words
The combination according to claim 1 wherein said compressing means comprises first and second variable loss devices connected so as to have the impedances thereof simultaneously varied by the direct-current control signal; said compressing means causing the voice signals and the pilot tone to be associated with different ones of said first and second variable loss devices for effecting compression and adjustment thereof.
Claim 5
Dependent Claim
49 words
The combination according to claim 3 wherein said last-named means which is at the receiving terminal includes a third variable loss device that is controlled in response to the adjusted pilot tone for effecting expansion of the compressed voice signals and compensation for losses caused by the transmission medium.
Claim 6
Dependent Claim
18 words
The combination according to claim 4 wherein said first, second, and third variable loss devices are diode variolossers.
Claim 7
Dependent Claim
25 words
The combination according to claim 5 wherein said first and second diode variolossers are connected in series to pass said direct current control signal therethrough.
Claim 8
Dependent Claim
42 words
The combination according to claim 6 wherein said second diode variolosser includes a pair of capacitors so connected to place the diodes thereof in series with respect to said direct current control signal and in parallel with respect to said pilot tone.
Claim 9
Dependent Claim
20 words
The combination according to claim 7 wherein said last-named means includes rectifying means selectively tuned to rectify said pilot tone.
Claim 10
Dependent Claim
31 words
The combination according to claim 8 wherein said last-named means includes a direct current amplifier responsive to the rectified pilot tone to vary the direct current through said third diode variolosser.
Claim 11
Dependent Claim
29 words
The combination according to claim 9 wherein said direct current amplifier is biased to provide a reference voltage level to regulate said third diode variolosser against said reference voltage.
Claim 12
Dependent Claim
20 words
The combination according to claim 10 wherein said pilot tone is a selected frequency ranging from 3400 to 6000 Hz.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-07-14 | 1979-01-13 | 1979-07-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-07-14 | 1983-01-13 | 1983-07-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-07-14 | 1987-01-13 | 1987-07-15 | $7700.00 | Window Closed / Lapsed |