US3743790A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Tee connection circuit for pcm telephone transmission systems
Assignee: BAE Systems Electronics Ltd
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Filing: 1971-05-28
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Granted: 1973-07-03
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Expires: 1991-05-28
Abstract
Abstract A pulse code modulated telephony transmission arrangement provides a facility which enables an operator to ''''tee'''' across an established connection between two subscribers without breaking the connection and without reducing the quality and audibility of the connection. The telephony transmission data from the subscribers and operator is of nonlinearly coded digital form and each is independently converted to linear coded digital signals which are then additionally mixed as required and thereafter converted back to the original nonlinearly coded digital form to permit the operator to speak to the subscribers, or to monitor the conversation. The digital mixing ensures both that no clicks will be heard by the subscribers, and that no reduction of signal level is produced when a ''''tee'''' connection is made.
Inventors
- 👤 R Hilsley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 01:30
CPC Classifications
H; H04; H04M; H04M3/00; H04M3/42; H04M3/56; H04M3/568; H04M3/561; H04Q; H04Q11/00; H04Q11/04
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
282 words
A ''''tee'''' connection circuit for adding signals in a PCM telephone transmission system in which a selected nonlinearly coded format is used, comprising in combination: first, second and third terminal pairs, one terminal of each pair receiving PCM voice signals of said selected nonlinearly coded format and the other terminal of each pair transmitting PCM voice signals of said selected nonlinearly coded format, a first serial path connected between said one terminal of said first terminal pair and said other teRminal of said second terminal pair, a second serial path connected between said one terminal of said second terminal pair and said other terminal of said first terminal pair; each serial path containing in the order stated; expander means for converting the nonlinearly coded PCM voice signals fed to it to corresponding linearly coded PCM signals; adder means for summing linearly coded PCM signals fed to it; compressor means for converting linearly coded PCM signals received thereby to transmitted PCM voice signals of said selected nonlinearly coded format; further adder means connected to receive both linearly coded PCM signals provided by the expander means of each said first and said second serial paths for summing these signals; further compressor means connected to said further adder means for converting summed linearly coded PCM signals provided by said further adder means to the nonlinearly coded format, and connected to supply these signals to said other terminal of the third terminal pair; further expander means for converting the nonlinearly coded signals received at the said one terminal of said third terminal pair to corresponding linearly coded PCM signals, which are fed to both of said adder means of said first and said second serial paths.
Claim 2
Dependent Claim
282 words
A ''''tee'''' connection circuit for adding signals in a PCM telephone transmission system in which a selected nonlinearly coded format is used, comprising in combination: first, second and third terminal pairs, one terminal of each pair receiving PCM voice signals of said selected nonlinearly coded format and the other terminal of each pair transmitting PCM voice signals of said selected nonlinearly coded format, a first serial path connected between said one terminal of said first terminal pair and said other teRminal of said second terminal pair, a second serial path connected between said one terminal of said second terminal pair and said other terminal of said first terminal pair; each serial path containing in the order stated; expander means for converting the nonlinearly coded PCM voice signals fed to it to corresponding linearly coded PCM signals; adder means for summing linearly coded PCM signals fed to it; compressor means for converting linearly coded PCM signals received thereby to transmitted PCM voice signals of said selected nonlinearly coded format; further adder means connected to receive both linearly coded PCM signals provided by the expander means of each said first and said second serial paths for summing these signals; further compressor means connected to said further adder means for converting summed linearly coded PCM signals provided by said further adder means to the nonlinearly coded format, and connected to supply these signals to said other terminal of the third terminal pair; further expander means for converting the nonlinearly coded signals received at the said one terminal of said third terminal pair to corresponding linearly coded PCM signals, which are fed to both of said adder means of said first and said second serial paths.
Claim 3
Dependent Claim
46 words
A ''''tee'''' connection circuit as defined in claim 1 including means for selectively connecting said one terminal of said first pair directly to said other terminal of said second pair and said other terminal of said first pair to said one terminal of said second pair.
Claim 4
Dependent Claim
17 words
A ''''tee'''' connection circuit as defined in claim 2 wherein the means last mentioned comprises inhibit gates.
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) | 1976-07-02 | 1977-01-01 | 1977-07-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-02 | 1981-01-01 | 1981-07-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-02 | 1985-01-01 | 1985-07-03 | $7700.00 | Window Closed / Lapsed |