Method of searching fault locations in digital transmission line

Claim 1

A method of searching fault locations in a transmission system comprising a transmitting terminal (1) having a transmitter (2) for transmitting a digital signal; a receiving terminal (5) having a receiver (8) for receiving the digital signal; a plurality of repeaters (4, 4 ...) which are placed between the transmitting and receiving terminals (1, 5), and each of which receives and amplifies the digital signal from a preceding repeater section and deliver it to a subsequent repeater section; and a plurality of transmission lines (3, 3, ...) for connecting the transmitter (2) with the first repeater (4), the repeaters (4) with each other, and the final repeater (4) with the receiver (8), respectively; said method comprising the steps of: coding an original signal to be transmitted in terms of two kinds of error detecting codes at the transmitting terminal (1) to send out them from the transmitter (2); detecting an error of a received signal using one of said two kinds of error detecting codes at each repeater thereby to measure the error rate occurred at one repeater section corresponding to each repeater; recoding a decoded received signal using said error detecting code employed to detect the error, and delivering it to a subsequent repeater section; and transmitting signals each of which represents said error rate at each repeater section measured at each repeater, to the transmitting terminal (1) or receiving terminal (5).

Claim 2

A method of searching fault locations in a transmission system comprising a transmitting terminal (1) having a transmitter (2) for transmitting a digital signal; a receiving terminal (5) having a receiver (8) for receiving the digital signal; a plurality of repeaters (4, 4 ...) which are placed between the transmitting and receiving terminals (1, 5), and each of which receives and amplifies the digital signal from a preceding repeater section and deliver it to a subsequent repeater section; and a plurality of transmission lines (3, 3, ...) for connecting the transmitter (2) with the first repeater (4), the repeaters (4) with each other, and the final repeater (4) with the receiver (8), respectively; said method comprising the steps of: coding an original signal to be transmitted in terms of two kinds of error detecting codes at the transmitting terminal (1) to send out them from the transmitter (2); detecting an error of a received signal using one of said two kinds of error detecting codes at each repeater thereby to measure the error rate occurred at one repeater section corresponding to each repeater; recoding a decoded received signal using said error detecting code employed to detect the error, and delivering it to a subsequent repeater section; and transmitting signals each of which represents said error rate at each repeater section measured at each repeater, to the transmitting terminal (1) or receiving terminal (5).

Claim 3

A method of searching fault locations in a transmission system comprising a transmitting terminal (1) having a transmitter (2) for transmitting a digital signal; a receiving terminal (5) having a receiver (8) for receiving the digital signal; a plurality of repeaters (4, 4, ...) which are placed between the transmitting and receiving terminals (1, 5), and each of which receives and amplifies the digital signal from a preceding repeater section and delivers it to a subsequent repeater section; and a plurality of transmission lines (3, 3, ...) for connecting the transmitter (2) with the first repeater (4), the repeaters (4) with each other, and the final repeater (4) with the receiver (8), respectively; said method comprising the steps of: coding an original signal to be transmitted in terms of two kinds of error detecting codes at the transmitting terminal (1) to send out them from the transmitter (2); detecting an error of a received signal using one of said two kinds of error detecting codes at each repeater thereby to measure the error rate occurred at one repeater section corresponding to each repeater; recoding a decoded received signal using said error detecting code employed to detect the error, and delivering it to a subsequent repeater section; transmitting signals each of which represents said error rate at each repeater section measured at each repeater, to the transmitting terminal (1) or receiving terminal (5); and detecting an error of a received signal using the other of said two kinds of error detecting codes at the receiving terminal thereby to.measure an overall error rate over the entire sections.

Claim 4

A method of searching fault locations in a transmission system comprising a transmitting terminal (1) having a transmitter (2) for transmitting a digital signal; a receiving terminal (5) having a receiver (8) for receiving the digital signal; a plurality of repeaters (4, 4, ...) which are placed between the transmitting and receiving terminals (1, 5), and each of which receives and amplifies the digital signal from a preceding repeater section and delivers it to a subsequent repeater section; and a plurality of transmission lines (3, 3, ...) for connecting the transmitter (2) with the first repeater (4), the repeaters (4) with each other, and the final repeater (4) with the receiver (8), respectively; said method comprising the steps of: coding an original signal to be transmitted in terms of two kinds of error detecting codes at the transmitting terminal (1) to send out them from the transmitter (2); detecting an error of a received signal using one of said two kinds of error detecting codes at each repeater thereby to measure the error rate occurred at one repeater section corresponding to each repeater; recoding a decoded received signal using said error detecting code employed to detect the error, and delivering it to a subsequent repeater section; transmitting signals each of which represents said error rate at each repeater section measured at each repeater, to the transmitting terminal (1) or receiving terminal (5); and detecting an error of a received signal using the other of said two kinds of error detecting codes at the receiving terminal thereby to.measure an overall error rate over the entire sections.

Claim 7

A method of searching fault locations in a transmission system according to any one of Claims 1 to 4 wherein said two kinds of error detecting codes are a parity code and an Alternate Mark Inversion (AMI) code.

Claim 8

A method of searching fault locations in a transmission system according to any one of Claims 1 to 4 wherein said two kinds of error detecting codes are a parity code and a two-level AMI code.

Claim 10

A method of searching fault locations in a transmission system according to any one of Claims 1 to 4 wherein said two kinds of error detecting codes are a parity code and a transition precode.

Claim 12

A method of searching fault locations in a transmission system according to any one of Claims 1 to 9, wherein said signals each of which represents said error rate at each repeater section measured at each repeater are of different frequencies for the respective repeaters. ll. A method of searching fault locations in a transmission system according to any one of Claims 1 to 10, wherein said signals each of which represents said error rate at each repeater section measured at each repeater are transmitted to said transmitting terminal or receiving terminal when said error rate exceeds a predetermined value.

Claim 14

A system for searching fault locations in a transmission system comprising a transmitting terminal (1) having a transmitter (2) for transmitting a digital signal; a receiving terminal (5) having a receiver (8) for receiving the digital signal; a plurality of repeaters (4, 4, ...) which are placed between the transmitting and receiving terminals (1, 5), and each of which receives and amplifies the digital signal from a preceding repeater section and deliver it to a subsequent repeater section; and a plurality of transmission lines (3, 3, ...) for connecting the transmitter (2) with the first repeater (4), the repeaters (4) with each other, and the final repeater (4) with the receiver (8), respectively; comprising: a transmitter provided with means for coding an original signal to be transmitted in terms of two kinds of error detecting code and serves to transmit the coded signals; a plurality of repeaters each of which is equipped with means for detecting an error of a received signal using one of said two kinds of error detecting codes thereby to measure the error rate occurred at one repeater section corresponding to each repeater, and means for recoding a decoded received signal using said error detecting code employed to detect the error, and delivering it to a subsequent repeater section; a receiver which is provided with means for detecting an error of a received signal using the other of said two kinds of error detecting codes thereby to measure an overall error rate of said transmission system and serves to receive the signals transmitted from said transmitter through said plurality of repeaters; a plurality of fault signal transmitters (6, 6,...) each of which is connected with each repeater and serves to transmit a fault signal representing the error rate of each repeater section measured by each repeater; a fault signal receiver (9, 10) which is installed in the transmitting terminal (1) or receiving terminal (5) and serves to receive said fault signals; and a transmission line for coupling said plurality of fault signal transmitters with said fault signal receiver.

Claim 15

A system for searching fault locations in a transmission system comprising a transmitting terminal (1) having a transmitter (2) for transmitting a digital signal; a receiving terminal (5) having a receiver (8) for receiving the digital signal; a plurality of repeaters (4, 4, ...) which are placed between the transmitting and receiving terminals (1, 5), and each of which receives and amplifies the digital signal from a preceding repeater section and deliver it to a subsequent repeater section; and a plurality of transmission lines (3, 3, ...) for connecting the transmitter (2) with the first repeater (4), the repeaters (4) with each other, and the final repeater (4) with the receiver (8), respectively; comprising: a transmitter provided with means for coding an original signal to be transmitted in terms of two kinds of error detecting code and serves to transmit the coded signals; a plurality of repeaters each of which is equipped with means for detecting an error of a received signal using one of said two kinds of error detecting codes thereby to measure the error rate occurred at one repeater section corresponding to each repeater, and means for recoding a decoded received signal using said error detecting code employed to detect the error, and delivering it to a subsequent repeater section; a receiver which is provided with means for detecting an error of a received signal using the other of said two kinds of error detecting codes thereby to measure an overall error rate of said transmission system and serves to receive the signals transmitted from said transmitter through said plurality of repeaters; a plurality of fault signal transmitters (6, 6,...) each of which is connected with each repeater and serves to transmit a fault signal representing the error rate of each repeater section measured by each repeater; a fault signal receiver (9, 10) which is installed in the transmitting terminal (1) or receiving terminal (5) and serves to receive said fault signals; and a transmission line for coupling said plurality of fault signal transmitters with said fault signal receiver.

Claim 19

A system for searching fault locations in a transmission system according to any one of Claims 13 to 16, wherein said plurality of fault signal transmitters transmit signals of different frequencies, respectively.

Claim 20

A system for searching fault locations in a transmission system according to any one of Claims 13 to 17, wherein each of said plurality of fault signal transmitters transmits a fault signal when the error rate of each repeater section measured by each repeater exceeds a predetermined value.