US3891806A
Expired / Lapsed
US
⏱️ 0.0 years remaining
System for preventing intelligible crosstalk in TDM switching systems
Assignee: International Standard Electric Corp
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Filing: 1973-11-28
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Granted: 1975-06-24
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Expires: 1993-11-28
Abstract
Abstract Apparatus is disclosed for protecting against intelligible crosstalk in a PCM-TDM system. Such crosstalk may arise when there is a failure in the system causing a mixing of signals in a first channel with signals from a second incoming channel. When the first channel is silent (sign bit zero and amplitude train zero) signals from the second channel may be added to the zero train causing the receiving subscriber of the first channel to receive undesirable crosstalk. To combat this situation, the invention employs two code conversion devices in series in a line. The first device inverts coded combinations having a sign bit 0 while transmitting without modification those with sign bit 1. The second device adjacent the output cancels the inversion of the first device to provide normal combinations to the called line.
Inventors
- 👤 Andre Edouard Joseph Chatelon
- 👤 Andre Lucien Coudray
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 13:27
CPC Classifications
H; H04; H04Q; H04Q11/00; H04Q11/04
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
173 words
A protective system to prevent the occurrence of intelligible crosstalk between time division channels comprising, code conversion means coupled near the inputs of a time division switching center, said code conversion means recieving incoming time division signals including a polarity bit and coded combinations of amplitude bits, said code conversion means transmitting the polarity bit unchanged, said code conversion means responding to a polarity bit of a first value to transmit the amplitude bits unchanged and to a polarity bit of the opposite value to invert the amplitude bits and then transmit them, and, complementary code conversion means coupled at the outputs of the center, said complementary code conversion means transmitting the polarity bit unchanged and inverting the amplitude bits of the coded combinations when the polarity bit has said particular value, whereby when one channel is silent, the coded combinations inserted into the center are never null or almost null, but on the contrary take values adapted to mask at least partly possible disturbing signals, and destroy intelligibility of said disturbing signals.
Claim 2
Dependent Claim
173 words
A protective system to prevent the occurrence of intelligible crosstalk between time division channels comprising, code conversion means coupled near the inputs of a time division switching center, said code conversion means recieving incoming time division signals including a polarity bit and coded combinations of amplitude bits, said code conversion means transmitting the polarity bit unchanged, said code conversion means responding to a polarity bit of a first value to transmit the amplitude bits unchanged and to a polarity bit of the opposite value to invert the amplitude bits and then transmit them, and, complementary code conversion means coupled at the outputs of the center, said complementary code conversion means transmitting the polarity bit unchanged and inverting the amplitude bits of the coded combinations when the polarity bit has said particular value, whereby when one channel is silent, the coded combinations inserted into the center are never null or almost null, but on the contrary take values adapted to mask at least partly possible disturbing signals, and destroy intelligibility of said disturbing signals.
Claim 3
Dependent Claim
87 words
The invention of claim 1, in which the code conversion means comprises a bistable circuit, said bistable circuit responds according to the value of the polarity bit of each coded combination to be set in one of its two positions, and two transmission paths arranged in parallel and conditioned respectively by the two complementary outputs of the bistable circuit, one of said two paths routing the bits defining the amplitude of the coded combinations without modifying them, while the other includes an inverter to invert said bits.
Claim 4
Dependent Claim
26 words
The invention of claim 1, in which said code conversion means are inserted into incoming and outgoing primary multiplex groups of a time division switching center.
References Cited (Backward Citations)
DE1940027A1
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-06-23 | 1978-12-23 | 1979-06-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-23 | 1982-12-23 | 1983-06-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-23 | 1986-12-23 | 1987-06-24 | $7700.00 | Window Closed / Lapsed |