US4564933A — Supervision of digital transmission systems

Claim 1

Independent Claim 115 words

A method of supervising a digital transmission system having two terminals interconnected by separate unidirectional paths, and at least one repeater interposed in and between said paths, comprising sending a loop-back signal for a loop-back condition from one of the terminals via one of the paths to the repeater and via the repeater and the other path back to the one terminal, sending a digital multi-bit test signal from the other terminal via the other path to the repeater, and controlling the mix of the bits of the test signal to change the loop-back condition in the repeater in such manner as to determine the test signal level in the repeater which caused the change.

Claim 2

Independent Claim 115 words

A method of supervising a digital transmission system having two terminals interconnected by separate unidirectional paths, and at least one repeater interposed in and between said paths, comprising sending a loop-back signal for a loop-back condition from one of the terminals via one of the paths to the repeater and via the repeater and the other path back to the one terminal, sending a digital multi-bit test signal from the other terminal via the other path to the repeater, and controlling the mix of the bits of the test signal to change the loop-back condition in the repeater in such manner as to determine the test signal level in the repeater which caused the change.

Claim 3

Dependent Claim 101 words

A digital transmission system having a pair of terminals, one or more repeaters and separate undirectional paths, comprising means for sending a loop-back signal to the repeater from one of the terminals for establishing a loop-back condition in the repeater, means for sending to the repeater a digital multi-bit test signal from the other terminal, the mix of the bits in the test signal being controlled, loop-back circuitry in the repeater sensitive to the test signal to change the loop-back condition in the repeater, and means at one of the terminals to determine the test signal level which caused the change.

Claim 4

Dependent Claim 101 words

A digital transmission system having a pair of terminals, one or more repeaters and separate undirectional paths, comprising means for sending a loop-back signal to the repeater from one of the terminals for establishing a loop-back condition in the repeater, means for sending to the repeater a digital multi-bit test signal from the other terminal, the mix of the bits in the test signal being controlled, loop-back circuitry in the repeater sensitive to the test signal to change the loop-back condition in the repeater, and means at one of the terminals to determine the test signal level which caused the change.

Claim 5

Dependent Claim 22 words

A system as claimed in claim 2, wherein the loop-back condition is first established and the test signal disables the loop-back condition.

Claim 6

Dependent Claim 21 words

A system as claimed in claim 2, wherein the loop-back signal comprises an M-bit word formed by two different bit patterns.

Claim 7

Dependent Claim 24 words

A system as claimed in claim 4, wherein the two different bit patterns are 101010 . . . and 110011001100 . . . .

Claim 8

Dependent Claim 28 words

A system as claimed in claim 4 wherein at the repeater the fundamental frequency B/M is filtered and used to control loop-on, B being the data bit rate.

Claim 9

Dependent Claim 31 words

A system as claimed in claim 4 wherein the word length is different for each repeater to produce in any repeater a frequency unique thereto for selecting that repeater to loop-back.

Claim 10

Dependent Claim 46 words

A system as claimed in claim 2, wherein the bit amplitude of the test signal in the repeater is determined by comparing a d.c. level derived from the test signal with a known d.c. level and varying the mix of the bits until said change occurs.

Claim 11

Dependent Claim 53 words

A system as claimed in claim 2, wherein the bit amplitude of the test signal is known, a predetermined d.c. level is produced by varying the mix of the bits of the test signal, and the known d.c. level is compared with an unknown d.c. level which is determined when said event occurs.

Claim 12

Dependent Claim 75 words

A system as claimed in claim 2, wherein in order to measure the signal level at a particular point in the system the fundamental frequency of the test signal is extracted at that point, compared with a standard locally generated voltage and the mix of bits in the test signal is changed until the comparison changes sign, and determining the signal level from a knowledge of the bit mix and the local generated standard voltage.

Claim 13

Independent Claim 119 words

A method of supervising or controlling a digital transmission system having at least one repeater in the transmission path, comprising sending to the repeater via the path a bit stream divided into identical words of zero disparity, each word being n bit long, filtering at least one of the fundamental and harmonic frequencies, deriving from the filtered signal in the repeater a first d.c. signal whose level is dependent on the mix of the bits, comparing the d.c. signal with a second d.c. signal in the repeater, and varying the mix of the bits during the comparison to establish the level of the first and second d.c. signals relative to one another by operating a switch in the repeater.

Claim 14

Independent Claim 119 words

A method of supervising or controlling a digital transmission system having at least one repeater in the transmission path, comprising sending to the repeater via the path a bit stream divided into identical words of zero disparity, each word being n bit long, filtering at least one of the fundamental and harmonic frequencies, deriving from the filtered signal in the repeater a first d.c. signal whose level is dependent on the mix of the bits, comparing the d.c. signal with a second d.c. signal in the repeater, and varying the mix of the bits during the comparison to establish the level of the first and second d.c. signals relative to one another by operating a switch in the repeater.

Claim 15

Dependent Claim 96 words

A repeater for a digital transmission system, the repeater having two digital regenerators for respectively separate unidirectional paths of the system, loop-back circuitry sensitive to receipt of a loop-back signal from a terminal of the system to establish a loop-back condition between the unidirectional paths of the system, and a first comparator arrangement which compares a reference signal level with another signal level derived from and representative of a succession of incoming multi-bit test signals with different Fourier transforms and in response thereto changes the loop-back condition when the compared signal levels bear a predetermined relationship.

Claim 16

Dependent Claim 96 words

A repeater for a digital transmission system, the repeater having two digital regenerators for respectively separate unidirectional paths of the system, loop-back circuitry sensitive to receipt of a loop-back signal from a terminal of the system to establish a loop-back condition between the unidirectional paths of the system, and a first comparator arrangement which compares a reference signal level with another signal level derived from and representative of a succession of incoming multi-bit test signals with different Fourier transforms and in response thereto changes the loop-back condition when the compared signal levels bear a predetermined relationship.

Claim 17

Dependent Claim 45 words

A repeater as claimed in claim 12, comprising a first broadband filter, an envelope detector and a second narrow band filter, in that order, to derive from the loopback signal a frequency unique to that repeater, and a third filter to select the test signal.

Claim 18

Dependent Claim 23 words

A repeater as claimed in claim 12, wherein the reference signal level is derived from the line supply voltage which powers the repeater.

Claim 19

Dependent Claim 50 words

A repeater as claimed in claim 12, including a second comparator arrangement which compares the level of the loop-back signal with a reference level and forwards the loop-back signal, when the compared signals bear a predetermined relationship, for further comparison with the received test signal to change the loop-back condition.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1989-01-13	1989-07-15	1990-01-14	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1993-01-13	1993-07-15	1994-01-14	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1997-01-13	1997-07-15	1998-01-14	$7700.00	Window Closed / Lapsed

Supervision of digital transmission systems

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