US3560660A
Expired / Lapsed
US
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Time-allocation communication system with scrambling network
Assignee: Italtel SpA
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Filing: 1968-12-16
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Granted: 1971-02-02
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Expires: 1988-12-16
Abstract
Abstract Telephone communication system wherein two groups of subscribers, associated with opposite terminals of a two-way trunk line, are selectively connectable to that trunk line for transmission or reception under the control of a train of stepping pulses generated during a signal-transmission period of an operating cycle or frame, the number m'''' of stepping pulses in that train (and therefore the number of subscriber lines so connectable in any one frame) being half the total number of subscribers in each group. A distribution signal, sent out at the beginning of a frame during an allocation period, consists of a succession of address pulses identifying the calling subscribers whose message samples are transmitted in coded form during the following transmission period. The stepping pulses are fed to a scrambler which, under the control of a random selector responsive to the combination of code pulses in the first several message samples transmitted during an immediately preceding frame, suppresses a continuously varying number of stepping pulses in the original train to give rise to a modified train with a reduced number m > OR = w of stepping pulses, w being the number of subscribers to be connected as determined from a count of address pulses in the distribution signal immediately preceding such transmission. The (m-w) supernumerary stepping pulses left over after the transmission of the w message samples are used to test hitherto idle subscribers for possible inclusion of their message samples during the next frame. During the occurence of these supernumerary stepping pulses, as well as between the termination of the foreshortened pulse train and the end of the transmission period, a noise code generator is connected to the trunk to transmit spurious message signals which at the receiving terminal are weeded out by an unscrambler under the control of another random selector responsive to the same combination of code pulses as the selector at the transmitting terminal.
Inventors
- 👤 Isidoro Poretti
- 👤 Gianmario Costa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 16:51
CPC Classifications
H; H04; H04K; H04K1/00; H04J; H04J3/00; H04J3/16; H04J3/1682; H04J3/1688; H04L; H04L9/00; H04L9/06; H04L9/0618; H04L9/0637; H04L9/065; H04L9/0656; H04L9/0662; H04L2209/00; H04L2209/08; H04L2209/12
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
392 words
In a two-way communication system comprising a trunk line with signal paths for transmission in opposite directions, a terminal at each end of said trunk line having a transmitting section and a receiving section, a group of n subscriber lines with outgoing and incoming branches respectively terminating at said transmitting section and said receiving section, timer means for periodically sampling the signal level on each of said outgoing branches, first switching means at said transmitting section for sequentially connecting a maximum number m'''' n/2 of outgoing branches to said trunk line during each operating cycle of said timer means, second switching means at said receiving section for sequentially connecting to m'''' incoming branches to said trunk line during successive time intervals of each operating cycle under the control of a distribution signal from the opposite terminal, and level-responsive means for enabling said first switching means to connect a variable number w of outgoing branches to said trunk line during a transmission period of the cycle following an allocation period reserved for the sending of said distribution signal to the opposite terminal, the combination therewith of a source of m'''' stepping pulses constituting an original pulse train generated during said transmission period, scrambler means at said transmitting section for foreshortening said original pulse train by random suppression of certain pulses thereof to produce a modified train of m stepping pulses wherein m is at least equal to w, first selector means at said transmitting section for establishing a random pattern of suppression in said scrambler means, first circuit means for delivering said modified train to said first switching means for successively delivering message signals from said w outgoing branches to said trunk line during said transmitting period, noise generating means controlled by said scrambler means for delivering spurious signals to said trunk line during gaps in said modified train due to suppressed original stepping pulses, unscrambler means at said receiving section for eliminating said spurious signals from signals received over said trunk line, second selector means at said receiving section for controlling said unscrambler means in step with the pattern of suppression of said scrambler means at the transmitting section of the opposite terminal, and second circuit means at said receiving section for directing genuine message signals from sAid trunk line to a number w of called subscribers identified by said distribution signal.
Claim 2
Dependent Claim
392 words
In a two-way communication system comprising a trunk line with signal paths for transmission in opposite directions, a terminal at each end of said trunk line having a transmitting section and a receiving section, a group of n subscriber lines with outgoing and incoming branches respectively terminating at said transmitting section and said receiving section, timer means for periodically sampling the signal level on each of said outgoing branches, first switching means at said transmitting section for sequentially connecting a maximum number m'''' n/2 of outgoing branches to said trunk line during each operating cycle of said timer means, second switching means at said receiving section for sequentially connecting to m'''' incoming branches to said trunk line during successive time intervals of each operating cycle under the control of a distribution signal from the opposite terminal, and level-responsive means for enabling said first switching means to connect a variable number w of outgoing branches to said trunk line during a transmission period of the cycle following an allocation period reserved for the sending of said distribution signal to the opposite terminal, the combination therewith of a source of m'''' stepping pulses constituting an original pulse train generated during said transmission period, scrambler means at said transmitting section for foreshortening said original pulse train by random suppression of certain pulses thereof to produce a modified train of m stepping pulses wherein m is at least equal to w, first selector means at said transmitting section for establishing a random pattern of suppression in said scrambler means, first circuit means for delivering said modified train to said first switching means for successively delivering message signals from said w outgoing branches to said trunk line during said transmitting period, noise generating means controlled by said scrambler means for delivering spurious signals to said trunk line during gaps in said modified train due to suppressed original stepping pulses, unscrambler means at said receiving section for eliminating said spurious signals from signals received over said trunk line, second selector means at said receiving section for controlling said unscrambler means in step with the pattern of suppression of said scrambler means at the transmitting section of the opposite terminal, and second circuit means at said receiving section for directing genuine message signals from sAid trunk line to a number w of called subscribers identified by said distribution signal.
Claim 3
Dependent Claim
111 words
The combination defined in claim 1 wherein said first switch means comprises a counting chain of n stages triggerable in a predetermined order by said m stepping pulses to open a transmission gate for passing a signal sample of a respective outgoing branch, routing means for selectively bypassing any of said stages whereby the transmission gate thereof remains closed, and a preselector chain of n cyclically interconnected stages for preparing selected stages of said counting chain under the control of said level-responsive means for triggering in an immediately following cycle, the stages of said preselector chain being connected for successive actuation by supernumerary (m-w) stepping pulses generated during said transmission period.
Claim 4
Dependent Claim
40 words
The combination defined in claim 2 further comprising control means responsive to said supernumerary stepping pulses for delivering said spurious signals from said noise generating means to said trunk line also during preselection of further stages of said counting chain.
Claim 5
Dependent Claim
60 words
The combination defined in claim 1 wherein said signal paths include coding means at said transmitting section and decoding means at said receiving section, said first and second selector means each including a set of switching devices responsive to individual bits of code combinations into which signals transmitted during certain of said time intervals are converted by said coding means.
Claim 6
Dependent Claim
47 words
The combination defined in claim 4 wherein said switching devices are provided with connections to said trunk line closable by said timer means during the initial time intervals of said transmission period, the total number of digital positions in said initial time intervals being equal to m/2.
Claim 7
Dependent Claim
60 words
The combination defined in claim 4 wherein said scrambler means and unscrambler means each include a counter for subscriber identifying pulses in said distribution signal and circuitry controlled by said counter for actuating a number of said switching devices equal to the count of said subscriber identifying pulses independently of the operating pattern of said first and second selector means.
Claim 8
Dependent Claim
50 words
The combination defined in claim 6 wherein said scrambler means and unscrambler means each comprises a shift register with m'''' stages, said switching devices numbering m'''' and being respectively connectable to the stages of said register, said circuitry including a logic network inserted between the register stages and said counter.
Claim 9
Dependent Claim
55 words
The combination defined in claim 7 wherein said logic network includes (m'''' - 1) OR gates with progressively diminishing numbers of inputs connected to corresponding combinations of (m'''' - 1) stage outputs of said counter and working into respective register stages, a further stage output of said counter being connected to a final register stage.
Claim 10
Dependent Claim
45 words
The combination defined in claim 8 wherein said final register stage at said transmitting section is provided with a first output for generating said modified train of stepping pulses and with a second output for producing an inverted pulse to control said noise generating means.
Claim 11
Dependent Claim
43 words
The combination defined in claim 4 further including a generator of clearing pulses for periodically restoring all said switching devices to a normal condition irrespectively of said code combinations, the recurrence period of said clearing pulses being substantially greater than said operating cycle.
References Cited (Backward Citations)
US2412964A
Cited
US3372237A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-02-01 | 1974-08-03 | 1975-02-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-02-01 | 1978-08-03 | 1979-02-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-02-01 | 1982-08-03 | 1983-02-02 | $7700.00 | Window Closed / Lapsed |