Timing extraction method and communication system

Claim 2

A communication system for digital data communication between a plurality of terminal stations through a transmission medium, the communication system comprising: transmission means for performing transmission of information data coded into a multilevel code signal having N (N being an integer greater than or equal to 3) levels through the transmission medium with a baud rate; and receiving means for receiving the information data from the transmission means through the transmission medium, the receiving means including, means for generating interim clock pulses having a frequency (N-1) times the baud rate and which interim clock pulses are synchronizing with a portion of crossing timings between a received multilevel code signal and a predetermined threshold level, means for selecting one of (N-1) trains of baud-rate clock pulses by discriminating a predetermined pattern with the (N-1) trains of the baud-rate, and extracting means for extracting the information data from the received multilevel code signal on basis of the one of (N-1) trains of baud-rate clock pulses. t

Claim 3

A communication system according to claim 1, wherein said extracting means includes: level discriminator outputting an interim data train which including the information data by discriminating the level of the received multilevel code signal at timings of the interim clocks, means for distinguishing one of said (N-1) trains of baud-rate clock pulses which indicate discriminative timings from other trains, and means for picking up data which are results of level discrimination in said level discriminator at said discriminative timings from said interim data train to output the information data.

Claim 4

A communication system according to claim 2, wherein said level discriminator outputs the interim data train decoded into binary code signals.

Claim 5

A communication system according to claim 2, wherein said picking-up means is a latch circuit latching the output of said level discriminator at timings indicated by said distinguishing means.

Claim 6

A communication system according to claim 1, wherein said extracting means includes: means for distinguishing one of said (N-1) trains of baud-rate clock pulses which indicate discriminative timings from other trains, level discriminator discriminating the level of the received multilevel signal at said discriminative timings to output the information data.

Claim 7

A communication system for digital data communication between a plurality of terminal stations through a transmission medium, the communication system comprising: transmission means for performing transmission of information data coded into a multilevel code signal having N (N being an integer greater than or equal to 3) levels through the transmission medium with a baud rate; and receiving means for receiving the information data from the transmission means through the transmission medium, the receiving means including, means for generating interim clock pulses having a frequency (N-1) times the baud rate and which interim clock pulses are synchronizing with a portion of crossing timings between a received multilevel code signal and a predetermined threshold level, and extracting means for extracting the information data from the received multilevel code signal on basis of one of (N-1) trains of baud-rate clock pulses obtained by using the interim clock pulses, wherein the one of (N-1) trains of baud-rate clock pulses is selected by changing the selection among the (N-1) trains of baud-rate clock pulses when an error signal is generated more frequently than a non-error signal.

Claim 8

A communication system for digital data communication between a plurality of terminal stations through a transmission medium, the communication system comprising: transmission means for performing transmission of information data coded into a multilevel code signal having N (N being an integer greater than or equal to 3) levels through the transmission medium with a baud rate; and receiving means for receiving the information data from the transmission means through the transmission medium, the receiving means including, means for generating interim clock pulses having a frequency (N-1) times the baud rate and which interim clock pulses are synchronizing with a portion of crossing timings between a received multilevel code signal and a predetermined threshold level, and extracting means for extracting the information data from the received multilevel code signal on basis of one of (N-1) trains of baud-rate clock pulses obtained by using the interim clock pulses, wherein the one of (N-1) trains of baud-rate clock pulses is selected by changing the selection among the (N-1) trains of baud-rate clock pulses when an error signal is generated more frequently than a non-error signal.

Claim 9

A communication system for transmitting N (N being an integer greater or equal to 3) level code signals at a predetermined baud rate clock between a private branch exchanger and a plurality of terminal stations through a transmission medium, the communication system comprising: a private branch exchanger which includes an interface circuit for transmitting the N level code signals so that crossing signals having crossing timings between the N level code signals and a predetermined threshold level are synchronizing with clock pulses having N-1 times frequency of the predetermined baud rate clock; and a plurality of terminal stations connected to the private branch exchanger via the transmission medium, each of the terminal stations including, means for detecting the crossing timings between the N level code signals received from the private branch exchanger and the predetermined threshold level, means for generating the clock pulses having N-1 times frequency of the predetermined baud rate clock, so that the clock pulses are synchronized with a portion of the crossing timings, means for generating a plurality of trains of baud rate clock pulses whose frequencies are equal to the baud rate, whose pulses are synchronous with a portion of the crossing timings and whose phases differ from one another according to being synchronous with different ones of the crossing timings by dividing the clock pulses having N-1 times frequency of the baud rate, means for discriminating information data with one of the trains of baud rate clock pulses and providing an output data pattern, and means for selecting the one of the trains of baud rate clock pulses by checking the output data pattern from the means for discriminating.

Claim 10

A communication system for transmitting N (N being an integer greater or equal to 3) level code signals at a predetermined baud rate clock between a private branch exchanger and a plurality of terminal stations through a transmission medium, the communication system comprising: a private branch exchanger which includes an interface circuit for transmitting the N level code signals so that crossing signals having crossing timings between the N level code signals and a predetermined threshold level are synchronizing with clock pulses having N-1 times frequency of the predetermined baud rate clock; and a plurality of terminal stations connected to the private branch exchanger via the transmission medium, each of the terminal stations including, means for detecting the crossing timings between the N level code signals received from the private branch exchanger and the predetermined threshold level, means for generating the clock pulses having N-1 times frequency of the predetermined baud rate clock, so that the clock pulses are synchronized with a portion of the crossing timings, means for generating a plurality of trains of baud rate clock pulses whose frequencies are equal to the baud rate, whose pulses are synchronous with a portion of the crossing timings and whose phases differ from one another according to being synchronous with different ones of the crossing timings by dividing the clock pulses having N-1 times frequency of the baud rate, means for discriminating information data with one of the trains of baud rate clock pulses and providing an output data pattern, and means for selecting the one of the trains of baud rate clock pulses by checking the output data pattern from the means for discriminating.

Claim 11

A communication system according to claim 7, wherein the selecting means includes, a detector detecting whether there is a predetermined data pattern within the output data pattern from the discriminating means, and a switch for selectively supplying the one of the trains of baud rate clock pulses to the means for discriminating according to a detecting result of the detector.

Claim 12

A communication system for transmitting N (N being an integer greater or equal to 3) level code signals at a predetermined baud rate clock between a private branch exchanger and a plurality of terminal stations through a transmission medium, the communication system comprising: a private branch exchange which includes an interface circuit for transmitting the N level code signals so that crossing signals having crossing timings between the N level code signals and a predetermined threshold level are synchronizing with clock pulses having N-1 times frequency of the predetermined baud rate clock, the N level code signals having a frame synchronization pattern every predetermined data length; and a plurality of terminal stations connected to the private branch exchanger via the transmission medium, each of the terminal stations including, means for detecting the crossing timings between the N level code signals received from the private branch exchanger and the predetermined threshold level, means for generating the clock pulses having N-1 times frequency of the predetermined baud rate clock, so that a portion of the clock pulses is synchronized with the crossing timings, means for generating a plurality of trains of baud rate clock pulses whose frequencies are equal to the baud rate, whose pulses are synchronous with a portion of the crossing timings and whose phases differ from one another according to being synchronous with different ones of the crossing timings by dividing the clock pulses having N-1 times frequency of the baud rate, means for discriminating information data with one of the trains of baud rate clock pulses, and means for selecting the one of the trains of baud rate clock pulses and supplying the one of the trains of baud rate clock pulses to the discriminating means by checking whether output data from the means for discriminating includes the frame synchronization patterns.

Claim 13

A communication system for transmitting N (N being an integer greater or equal to 3) level code signals at a predetermined baud rate clock between a private branch exchanger and a plurality of terminal stations through a transmission medium, the communication system comprising: a private branch exchange which includes an interface circuit for transmitting the N level code signals so that crossing signals having crossing timings between the N level code signals and a predetermined threshold level are synchronizing with clock pulses having N-1 times frequency of the predetermined baud rate clock, the N level code signals having a frame synchronization pattern every predetermined data length; and a plurality of terminal stations connected to the private branch exchanger via the transmission medium, each of the terminal stations including, means for detecting the crossing timings between the N level code signals received from the private branch exchanger and the predetermined threshold level, means for generating the clock pulses having N-1 times frequency of the predetermined baud rate clock, so that a portion of the clock pulses is synchronized with the crossing timings, means for generating a plurality of trains of baud rate clock pulses whose frequencies are equal to the baud rate, whose pulses are synchronous with a portion of the crossing timings and whose phases differ from one another according to being synchronous with different ones of the crossing timings by dividing the clock pulses having N-1 times frequency of the baud rate, means for discriminating information data with one of the trains of baud rate clock pulses, and means for selecting the one of the trains of baud rate clock pulses and supplying the one of the trains of baud rate clock pulses to the discriminating means by checking whether output data from the means for discriminating includes the frame synchronization patterns.

Claim 14

A communication system for transmitting N (N being an integer greater or equal to 3) level code signals at a predetermined baud rate clock between a private branch exchanger and a plurality of terminal stations through a transmission medium, the communication system comprising: a private branch exchanger which includes an interface circuit for transmitting the N level code signals so that crossing signals having crossing timings between the N-level code signals and a predetermined threshold level are synchronizing with clock pulses having N-1 times frequency of the predetermined baud rate clock; and a plurality of terminal stations connected to the private branch exchanger via the transmission medium, each of the terminal stations including, means for detecting the crossing timings between the N level code signals received from the private branch exchanger and the predetermined threshold level, means for generating the clock pulses having N-1 times frequency of the predetermined baud rate clock, so that the clock pulses are synchronizing with a portion of the crossing timings, means for generating a plurality of trains of baud rate clock pulses whose frequencies are equal to the baud rate, whose pulses are synchronous with a portion of the crossing timings and whose phases differ from one another according to being synchronous with different ones of the crossing timings by dividing the clock pulses having N-1 times frequency of the baud rate, means for discriminating interim data including information data with the clock pulses having N-1 times frequency of the predetermined baud rate clock, means for selecting one of the trains of baud rate clock pulses by checking every data pattern obtained by discriminating the interim data with every one of the trains of baud rate clock pulses, and means for discriminating information data obtained by latching the interim data with the one of the trains of baud rate clock pulses selected by the selecting means.

Claim 15

A communication system for transmitting N (N being an integer greater or equal to 3) level code signals at a predetermined baud rate clock between a private branch exchanger and a plurality of terminal stations through a transmission medium, the communication system comprising: a private branch exchanger which includes an interface circuit for transmitting the N level code signals so that crossing signals having crossing timings between the N-level code signals and a predetermined threshold level are synchronizing with clock pulses having N-1 times frequency of the predetermined baud rate clock; and a plurality of terminal stations connected to the private branch exchanger via the transmission medium, each of the terminal stations including, means for detecting the crossing timings between the N level code signals received from the private branch exchanger and the predetermined threshold level, means for generating the clock pulses having N-1 times frequency of the predetermined baud rate clock, so that the clock pulses are synchronizing with a portion of the crossing timings, means for generating a plurality of trains of baud rate clock pulses whose frequencies are equal to the baud rate, whose pulses are synchronous with a portion of the crossing timings and whose phases differ from one another according to being synchronous with different ones of the crossing timings by dividing the clock pulses having N-1 times frequency of the baud rate, means for discriminating interim data including information data with the clock pulses having N-1 times frequency of the predetermined baud rate clock, means for selecting one of the trains of baud rate clock pulses by checking every data pattern obtained by discriminating the interim data with every one of the trains of baud rate clock pulses, and means for discriminating information data obtained by latching the interim data with the one of the trains of baud rate clock pulses selected by the selecting means.

Claim 16

A communication system according to claim 10, wherein the means for selecting includes, a plurality of frame synchronizers for comparing a predetermined data pattern and every data pattern extracted from the interim data with every one of the trains of baud rate clock pulses, and a selector for selecting the one of the trains of baud rate clock pulses according to a result of comparison by every one of the frame synchronizers.

Claim 17

A communication system for transmitting N (N being an integer greater or equal to 3) level code signals at a predetermined baud rate clock between a private branch exchanger and a plurality of terminal stations through a transmission medium, the communication system comprising: a private branch exchanger which includes an interface circuit for transmitting the N level code signals so that crossing signals having crossing timings between the N level code signals and a predetermined threshold level are synchronizing with clock pulses having N-1 times frequency of the predetermined baud rate clock, the N level code signals having a frame synchronization pattern every predetermined data length, and a plurality of terminal stations connected to the private branch exchanger via the transmission medium, each of the terminal stations including, means for detecting the crossing timings between the N level code signals received from the private branch exchanger and the predetermined threshold level, means for generating the clock pulses having N-1 times frequency of the predetermined baud rate clock, so that a portion of the clock pulses is synchronized with the crossing timings, means for discriminating interim data from N level code signals with the clock pulses having N-1 times frequency of the predetermined baud rate clock, means for comparing every one of plural data patterns obtained by de-interleaving the interim data and a predetermined frame synchronization data pattern, means for generating baud rate clock pulses from the clock pulses having N-1 times frequency of the baud rate clock according to a result of the means for comparing, and means for extracting information data from interim data with the baud rate clock.

Claim 18

A communication system for transmitting N (N being an integer greater or equal to 3) level code signals at a predetermined baud rate clock between a private branch exchanger and a plurality of terminal stations through a transmission medium, the communication system comprising: a private branch exchanger which includes an interface circuit for transmitting the N level code signals so that crossing signals having crossing timings between the N level code signals and a predetermined threshold level are synchronizing with clock pulses having N-1 times frequency of the predetermined baud rate clock, the N level code signals having a frame synchronization pattern every predetermined data length, and a plurality of terminal stations connected to the private branch exchanger via the transmission medium, each of the terminal stations including, means for detecting the crossing timings between the N level code signals received from the private branch exchanger and the predetermined threshold level, means for generating the clock pulses having N-1 times frequency of the predetermined baud rate clock, so that a portion of the clock pulses is synchronized with the crossing timings, means for discriminating interim data from N level code signals with the clock pulses having N-1 times frequency of the predetermined baud rate clock, means for comparing every one of plural data patterns obtained by de-interleaving the interim data and a predetermined frame synchronization data pattern, means for generating baud rate clock pulses from the clock pulses having N-1 times frequency of the baud rate clock according to a result of the means for comparing, and means for extracting information data from interim data with the baud rate clock.