FR2782590A1 - Transmission and receiving apparatus for rapid restoration of data transmission after temporary interruption, uses two counters to control the institution and cancellation of a hold signal - Google Patents

Abstract

The transmission and receiving apparatus for a communications network uses an output device for outputting hold signals, a detector (113), and a hold setting / canceling device (114b). When a signal is interrupted on a transmission line, this is detected and two counters (142,143) are initiated. When either of these two counter reach finishes counting, the holding of parameters is canceled, restoring a data transmission when a line interruption occurs. The hold setting / canceling device consists of a 2.5 second counter (142) from the restoration of the carrier, and a 15-second counter (143) from the interruption of the carrier signal. Additionally, a sum unit (144,145) is connected to the two counters, providing a hold signal that is the sum of the two counter outputs. Once one of the two counters reach zero, the sum is defunct, and the hold signal is withdrawn. An Independent claim is included for a method of coping with a momentary line interruption.

Description

BACKGROUND OF THE INVENTION

  Field of the Invention The present invention relates to a method allowing rapid restoration after a momentary line interruption when such an interruption occurs in data transmission devices such as a modem, etc. The present invention also relates to a device to deal with such an interruption of

momentary line.

Description of the Prior Art

  Sometimes a temporary interruption of data transmission signals due to the failure of a communications network

  communication etc ... happen and a certain variety of counter

measures have been reviewed.

  Conventionally, a modem has always monitored whether or not a carrier for data transmission signals transmitted in a communication network is interrupted, that is to say whether or not the carrier is received. When the carrier is interrupted (when it becomes disconnected), a certain variety of established modem parameters are saved while when the carrier becomes activated, i.e. when the carrier is normally received,

  saving the variety of parameters is canceled.

  Figures 1 and 2 are timing diagrams which show this process in more detail. FIG. 1 represents a process in the case where a carrier cut-off period is shorter than a predetermined time limit. FIG. 2 represents a process in the case where the time of the carrier cut-off period is longer than the time limit allowed. A time limit is a time after which a quick restore process is abandoned and the saving of the variety of parameters is canceled when the carrier interruption continues for a time longer than an arbitrary predetermined time.

  First, Figure 1 is described.

  Inside the modem, the configuration is such that while a carrier signal is received, a carrier pseudo-detection signal (CD) becomes active while when this same carrier signal is not received, the carrier pseudo-detection signal becomes cut. In the case of FIG. 1 also, when the carrier signal becomes cut, that is to say when the carrier signal stops receiving, the carrier pseudo-detection signal goes from the state activated in the off state. Since from the moment when the carrier cut is detected until the time when the carrier pseudo-detection signal becomes cut, a time delay due to the process inside the modem occurs, there is a delay in the modem from the instant when the carrier signal becomes interrupted until the instant when the pseudo-carrier detection signal becomes interrupted as

shown in figure 1.

  From the moment the carrier signal becomes cut, signals cannot be received normally, and the received data changes from a normal state to an abnormal state. When the signal of pseudo-detection of carrier becomes cut, simultaneously a backup signal to request in instruction cancellation of the backup of the variety of parameters of the modem passes from a state

normal to an abnormal state.

  When the carrier becomes activated before the time limit has elapsed, the carrier pseudo-detection signal becomes activated after the delay time in the modem has elapsed. Then the backup signal goes from a backup state to a normal state and the received data is restored from an abnormal state to a normal state. In this way, after the carrier is restored to the activated state, normal data reception can be

restarted quickly.

  Furthermore, the case shown in Figure 2 is as follows.

  The process in the case where the carrier becomes cut is the same as that in FIG. 1. When the carrier does not become activated after the time limit has elapsed, the pseudo-carrier detection signal is forced to become activated . Here, a timer is used to assess whether or not the time limit has elapsed. When the counting performed by the timer exceeds the time limit, the carrier pseudo-detection signal becomes activated. Then the backup signal goes from a backup state to a normal state. By means of the transition to the normal state of the backup signal, the parameters of the variety of parameters

saved are set to zero.

  In this case, after the carrier becomes activated, the modem is "hooked" again (it is synchronized with a signal from the opposite station) and after that the parameters in each part

  re-established, data reception is restarted.

  According to conventional countermeasures against a momentary line interruption, a certain variety of modem parameters are saved on the basis of a carrier pseudo-detection signal. That is, when the carrier pseudo-detection signal becomes disabled, the parameters of the variety of parameters

  are saved simultaneously and when the pseudo signal

  carrier detection becomes enabled, backups of the variety of

  saved parameters are canceled simultaneously.

  In this case, there is a high risk that the problems that

follow may occur.

  The modem often extracts a timing signal from signals received from the opposite station and controls its own operation to synchronize with the extracted timing signal. However, in this case, since the modem cannot receive signals from the opposite station while the data transmission signals are interrupted, it cannot extract the timing signal. For this reason, the modem operates in freewheel mode using its own clock timing which is based on the timing signal extracted before the interruption. In this way, during the interruption, since the modem cannot receive a timing signal from the opposite station and it operates on the basis of its own clock, the

  synchronization with the opposite station cannot be maintained.

  Since after the end of the interrupt (after restoring signals), the modem can receive signals from the opposite station, the modem can extract a timing signal from the opposite station and restore synchronization

  with the opposite station becomes possible.

  Since the operating timing at the time of freewheeling operation of the modem during the interruption is based on its own clock, a slight deviation occurs between the operating timing and that of the opposite station. For this reason, there is a risk that the newly extracted timing signal after the end of the interruption and that the timing of operation at the time of coasting operation of the modem may be deviated. Although the modem attempts to execute a variety of its processes with this deviated timing as it is, it cannot execute them due to the deviated timing and a long time is consumed for synchronization to be restored, which is a problem. . During this period, the modem cannot receive

  data normally and an error occurs.

  From the moment the carrier is interrupted and the modem appreciates that a short interruption occurs until the parameters of the variety of parameters are saved, a delay in the modem occurs. For this reason, strictly speaking, a deviation is also generated between the saved parameters and those at the moment when the carrier becomes cut. If the backup is canceled at the time of the end of the interruption under these conditions, a long time is consumed for synchronization to be restored due to the existence of a deviation between the parameters and there will be risk of data error occurring for some time

  after the interruption has ended.

  Summary of the Invention It is an object of the present invention to provide a method and apparatus for transmitting data for rapid restoration after a momentary line interruption when such an interruption occurs in a transmission apparatus

  using the prior arts described above.

  In order to achieve this object, an apparatus for transmitting and receiving data via a communication network which is one of the preferred embodiments of the present invention includes an output unit for transmitting in output a plurality of backup signals to request instruction to save / cancel a backup of a plurality of parameters related to an operation of receiving data transmitted via the communication network, a detection unit for detecting existence / non-existence of signals transmitted via the communication network, a backup establishment unit for saving the parameters in accordance with instructions of the backup signals when the detection unit detects non-existence of the signals, and a backup canceling setting unit for canceling the saving of the parameters in the order co in accordance with the instructions of the backup signals when the detection unit detects an existence of the signals after the detection unit detects the non

existence of signals.

  Among the parameters related to the reception operation, there are parameters which should cancel the backup immediately after the carrier is restored following the line interruption and there are parameters whose fluctuations can be reduced in a time shorter if the backup is canceled after the fluctuations in other parameters have been reduced. The configuration described above also makes it possible to cancel the saving in an appropriate order according to the characteristics of each parameter without canceling the saving of a plurality of parameters simultaneously and as a result, the time necessary for the fluctuations of each parameter is reduced and that a reception of

  normal data can be restored can be reduced.

  In the configuration described above, the backup cancellation establishment unit can also be configured so as to establish the backup cancellation of the parameters in a different order from that which is established when the detector unit detects newly the existence of the signals before a prescribed time has elapsed, in accordance with the instructions of the plurality of backup signals, when the detector unit continues to detect the non

  existence of signals after the prescribed time has elapsed.

  The fluctuations of the parameters reported to the reception operation are often reduced more quickly if an order at the level of the cancellation of saving of the parameters is modified according to the length of the line interruption period. In the configuration described above, the saving of groups of parameters by means of such characteristics can be canceled in an appropriate order depending on the length of the interruption period and as a result, a time necessary for the fluctuations of each parameter is reduced and so that a data reception

  normal be restored can be reduced.

Brief description of the drawings

  The present invention will appear more clearly in view

  of the detailed description which follows which will be read in conjunction with the

  appended drawings among which: FIG. 1 is a timing diagram which represents conventional countermeasures vis-à-vis a momentary line interruption (number 1); FIG. 2 is a timing diagram which represents conventional countermeasures against a momentary line interruption (number 2); FIG. 3 represents the mode of connection of modems; Figure 4 shows the configuration of a modem which constitutes a preferred embodiment of the present invention; Figure 5 shows the configuration of a momentary interrupt processing unit according to a first preferred embodiment of the present invention; Figure 6 is a timing diagram showing the operation of the momentary interrupt processing unit shown in Figure 5 (number 1); Figure 7 is a timing diagram showing the operation of the momentary interrupt processing unit shown in Figure 5 (number 2); Figure 8 shows the configuration of a momentary interrupt processing unit according to a second preferred embodiment of the present invention; FIG. 9 represents the control target of each backup signal; Figure 10 is a timing diagram showing the operation of the momentary interrupt processing unit shown in Figure 8 (number 1); Figure 11 is a timing diagram showing the operation of the momentary interrupt processing unit shown in Figure 8 (number 2); Figure 12 shows the configuration of a momentary interrupt processing unit according to a third preferred embodiment of the present invention; Figure 13 is a timing diagram showing the operation of the momentary interrupt processing unit shown in Figure 12 (number 1); and Figure 14 is a timing diagram showing the operation of the momentary interrupt processing unit

  shown in Figure 12 (number 2).

  Description of the preferred embodiments

  Figure 3 shows the modem connection mode. In FIG. 3, a parent station modem 12 and a child station modem 14 are connected via a network 13 so as to face each other, and data terminal equipment ( DTE) 11 and 15 are respectively connected to the parent station and child station modems 12 and 14. In the example shown in FIG. 3, the parent station modem 12 operates synchronously with a send timing signal ST1 which is transmitted from the DTE 11. The child station modem 14 extracts a timing element from signals received from the parent station modem 12 and operates on the basis of the received timing signal (RT)

extract.

  Figure 4 shows the configuration of a modem which constitutes a preferred embodiment of the present invention. A modem 20 shown in Figure 4 transmits and receives data using a quadrature amplitude modulation (QAM) of 768 values and has a general modem configuration with the exception of a pseudo-detection generator unit carrier 113 and a momentary interrupt processing unit 114 related to the present invention. Regarding the process of each unit, a digital signal process is carried out. Modem 20 is roughly

  divided into a receiver unit 21 and a transmitter unit 22.

  When the modem shown in Figure 4 is used for the parent station modem shown in Figure 3, the left and right sides of

  FIG. 4 are respectively connected to DTE 11 and to network 13.

  First, the receiver unit 21 of the modem 20 shown

in Figure 4 is described.

  Analog signals received from network 14 are converted to digital signals by an analog-to-digital converter (A / D) unit 101. Then these digital signals pass through a line equalizer (LEQ) unit 102 in order to correct so essentially adaptive attenuation of the high pass frequency due to the network for transmission signals and are demodulated according to baseband signals by a unit of

demodulator 103.

  The demodulated signals are transferred over a phase locked loop (PLL) ST2 104. The PLL ST2 104 performs a control so as to maintain a constant phase relationship between the modulated signals and the current operating clock of the modem. A cutoff filter (ROF) 105 is called a decimation filter, which filters the sampling frequency of the signals.

  modules that have passed through PLL ST2 104.

  The signals which have passed through ROF 105 are controlled so as to be at a constant signal level by an automatic gain control unit (AGC) 106 and in addition the influence of a transmission system such as a network etc ... is eliminated by the adaptive control of the equalizer unit (EQL) 107 and the resulting signals are routed to a control unit

  automatic carrier phase (CAPC) 108.

  The signals that are input to CAPC 108 are multi-value amplitude-quadrature data and are controlled by CAPC 108 to keep the signal constant.

  carrier wave phase modulated in amplitude in quadrature.

  The multi-modulated digital data of the signals output from the CAPC 108 is appreciated and extracted by a judgment unit 109 and the original digital data is applied to the DTE via a

logic processor 110.

  A signal to save / cancel the saving of each parameter is transmitted from the assessment unit 109 on both the EQL 107 and the CAPC 108 (as shown in (5) in FIG. 4). The

  detail of this backup signal (5) is described later.

  The modulated signals which have passed through the PLL ST2 104 are routed to both a timing extractor unit (TIM) 111 and a carrier pseudo-detection generator unit 113. The timing extractor unit (TIM) 111 extracts a signal

  timing from modulated signals.

  A PLL RT 112 is a digital PLL making it possible to generate an operating clock for the modem 20 taken as a whole and it establishes a synchronization with the extracted timing signal. Part of the clock generated by the PLL RT 112 is used as the sampling timing signal

  for the A / D converter unit 101.

  The carrier pseudo-detection generator unit 113 detects the existence / non-existence of a carrier for the modulated signals. If there is a carrier, the output becomes activated (it takes the level "H" or high) while if this is not the case, the output becomes

  cut (it takes level "L" or low).

  The short interrupt processing unit 114 reported to the

  The present invention is described below.

  The transmitter unit 22 of the modem 20 shown in Figure 4 is first described. The digital data that is received from the DTE is converted to multi-value QAM signals by the logic processor unit 124, then the signal band is limited by the cutoff filter (ROF) 123, the signals are modulated according to transmission band signals by a modulator unit 122, they are converted to analog signals by

  a D / A converter 121 and they are transmitted to the network 13.

  FIG. 5 shows the configuration of a momentary interrupt processing unit 114a in the modem which constitutes a first preferred embodiment of the present invention. Configuration is an example of the interrupt processing unit

  short 114 shown in Figure 4.

  In Figure 5, a carrier pseudo-detection signal is

  entered on a counter at 15 seconds 131.

  The 15-second counter 131 starts counting when the carrier pseudo-detection signal becomes cut and the output becomes activated when a period during which the carrier pseudo-detection signal is cut continues for 15 seconds after the start of the counting even if the output is cut off during counting. During a period during which the carrier pseudo-detection signal is activated, the activated state is maintained regardless of the existence / non-existence of the counting. The 15

  seconds correspond to the time limit described above.

  A 2.5-second counter 132 starts counting when the 15-second counter output 131 becomes activated and it becomes activated again after 2.5 seconds have elapsed after counting has started even if the output is cut during counting. The counter output at 2.5 seconds 132 is always

  cut while the 15 second counter 131 is cut.

  The output of the counter at 15 seconds 131 is used as a backup signal A. The output of the counter at 2.5 seconds 132 is used as a backup signal B. The operation of the momentary interrupt processing unit 114a shown in Figure 5 is described using

timing diagrams.

  Figures 6 and 7 are timing diagrams showing the operation of the interrupt processing unit

  short 114a shown in Figure 5.

  FIG. 6 represents a case in which a period during which the carrier is cut (the pseudo-detection signal of the carrier is cut) is less than the time limit allowed (15 seconds). When the carrier is interrupted and an internal delay time elapses (since the delay is due to the process of the carrier pseudo-detection generator unit 113 etc ... and the delay is only slight by comparison with the delay in the modem described above, the end of this delay time can be considered to be substantially simultaneous with the interruption of the carrier), the pseudo-carrier detection signal is cut. When the carrier pseudo-detection signal becomes interrupted, the counter at 15

  seconds 131 and the backup signals A and B become cut off.

  Simultaneously, the 15-second counter 131 starts counting. If the carrier is restored before a time of seconds has elapsed, the carrier pseudo-detection signal becomes activated after the internal delay time has elapsed. Then the output of the counter at 15 seconds 131 becomes activated and simultaneously, the backup signal A passes from a backup state to a backup cancellation state (represented as a normal state in FIG. 6). If the 15 second counter output 131 becomes activated, the 2.5 second counter 132 starts counting and the 2.5 second counter output 132 becomes activated after 2.5 seconds have elapsed. Then the backup signal B goes into a backup cancellation state (represented as a normal state on

Figure 6).

  FIG. 7 is different from the case in FIG. 6 and it represents a case in which a carrier cut-off period exceeds the

time limit (15 seconds).

  The operation at the time of a carrier interruption is the same as that shown in FIG. 6. When the carrier is interrupted, the carrier pseudo-detection signal becomes cut off after the internal delay time has elapsed , the 15 second counter 131 and the 2.5 second counter 132 both become cut off and the save signals A and B change to a save state. Then the counter at 15 seconds 131 starts counting. If 15 seconds elapse before the carrier is restored, the 15 second counter 131 ends the 15 second count and the output becomes activated, then the save signal A

goes into a normal state.

  When the 15-second counter 131 finishes counting 15 seconds, the 2.5-second counter 132 starts counting. Then, if 2.5 seconds elapse, the counter at 2.5 seconds 132, that is to say the backup signal B, passes into a

normal state.

  In this way, the backup signal B always goes into a normal state 2.5 seconds later than the backup signal A

  regardless of the length of the carrier recovery time.

  For example, the backup signal A is suitable for controlling the rapid cancellation of the backup of the targets after a carrier restoration and the backup signal B is used to control the cancellation of the backup of the targets for a prescribed time after the restoration of carrier since there is accompaniment by an “attachment” operation, etc. In the configuration shown in FIG. 4, a backup signal A is used to save / cancel the saving of a parameter for the information of phase of the PLL RT 112, a gain control parameter for the AGC 106 and a correction parameter for the LEQ 102, and a save signal B is used to save / cancel the saving of a parameter frequency information for the PLL RT 112 and each of the control parameters for the PLL ST 204,

EQL 107 and CAPC 108.

  FIG. 8 represents the configuration of a momentary interruption processing unit 114b according to a second embodiment

  preferred of the present invention.

  According to this preferred embodiment, five types of backup signals, namely backup signals (1) to (5), are established

as shown in figure 4.

  Figure 9 shows the control targets for each

backup signal.

  As shown in FIG. 9, the control targets for each of the backup signals are different. The backup signal (1) is for the PLL RT 112 and more particularly, it controls the phase information. The save signal (3) is also for the PLL RT 112 but it controls the frequency information. In PLL RT 112, when synchronization with signals from the opposite station cannot be obtained due to a momentary interruption, the synchronization deviation is considered to be slight if the interruption period is short. In this case, the frequency synchronization is practically maintained and it suffices to carry out essentially only phase synchronization after the restoration of the carrier which follows the interruption. If the interruption period is long, after the carrier restoration following the interruption, the first

  frequency synchronization is performed.

  The backup signal (2) controls the PLL ST2 104, the EQL

107 and CAPC 108.

  The save signal (4) - controls the AGC 106 and LEQ 102. In the AGC 106 and LEQ 102, it is possible that a significant deviation may occur between the saved parameters due to a delay in the modem since when the carrier is interrupted until a parameter is saved. For this reason, the AGC 106 and the LEQ 102 are also designed so that a

  "latching" starts after the interruption ends The backup signal (5) controls both the EQL 107 and the CAPC 108.

  When a signal level entered on the appreciation unit 111 is lower than a prescribed value, according to this preferred embodiment, and when the appreciation result is one of four points near an origin in a 768-value QAM signal, the signal

  backup (5) saves the parameter to be controlled.

  Then the conditions of each backup signal output

  are described using Figure 8.

  When a carrier is input to the carrier pseudo-detection generator unit 113, a carrier pseudo-detection signal is output based on specific conditions. If it is assumed that a difference between the amplitude of the carrier and a threshold is worth A, the signal of pseudo-detection of carrier becomes activated (it takes the level "H"), if the value of A is worth 0 or plus (0 or a positive value). If A is negative, the carrier pseudo-detection signal

  becomes cut (it takes the "L" level).

  The carrier pseudo-detection signal which is output from the carrier pseudo-detection signal generator unit 113 is entered on a logic product unit 141, on a counter at 2.5 seconds 142, on a counter at 15 seconds 143 and

  on a logical sum unit (OU) 145.

  On the logic product unit 141, an RT signal is entered in association with the carrier pseudo-detection signal. The RT signal indicates the operating mode of a modem. If the modem is established in RT mode, that is to say a mode in which it operates on the basis of signals received from the opposite station, RT becomes activated (level "H") and if it is not the case, it becomes cut (level "L"). The logic product unit 141 includes for example an AND circuit and a NON circuit, and the output is used as a backup signal (1). The logic product unit 141 is configured so that this backup signal (1) goes into a backup state (level "L") when RT is activated and the carrier pseudo-detection signal is cut off and qu '' he goes into a state

  normal ("H" level) under conditions other than these.

  The 2.5-second counter 142 counts the period during which the carrier pseudo-detection signal is activated. The output of the counter at 2.5 seconds 142 becomes activated (level "H") when the period of activation of the carrier pseudo-detection signal continues for more than 2.5 seconds and this same output becomes cut off (level " L ") either when the cut-off period of the carrier pseudo-detection signal is less than 2.5 seconds, or when the period of activation of the pseudo-detection signal of

  carrier is less than 2.5 seconds.

  The 15-second counter 143 counts the cut-off period of the carrier pseudo-detection signal. The output of the 15-second counter 143 shown in FIG. 8 becomes activated either when the cut-off period of the carrier pseudo-detection signal continues for more than 15 seconds, or while the carrier pseudo-detection signal is activated and this same output becomes cut off when the pseudo-detection signal cut-off period

  carrier time is less than 15 seconds.

  Each of the outputs of the 2.5-second counter 142 and the 15-second counter 143 is entered on a logical sum unit 144. The logical sum unit 144 comprises for example a

  OR circuit and its output is used as a backup signal (2).

  The OR unit 144 is configured so that the backup signal (2) goes into a normal state ("H" level) when either the counter output at 2.5 seconds 142 or the counter output at 15 seconds 143 is activated and this same signal goes to the backup state (level "L") in the other case (when the outputs of the

  counters 142 and 143 are both cut).

  The output of the logical sum unit 144 and the reception timing of RT are both entered on a logical product unit 146. The logical product unit 146 comprises for example an AND circuit and a NON circuit and the output is used as a backup signal (3). This backup signal (3) goes into a backup state when RT is activated and the output of the logical sum unit 144, i.e. the backup signal (2), goes into a state of backup and this same signal goes into a normal state in

a case other than this.

  The carrier pseudo-detection signal and the 15-second counter output 143 are both input to the logical sum unit 145. The output of the logical sum unit 145 is used as the backup signal (4 ). The logical sum unit comprises for example an OR circuit and the backup signal (4)

  goes into a backup state when the pseudo- signal

  carrier detection and the counter output at 15 seconds 143 are both cut off and this same signal goes into a normal state in

a case other than this.

  The result of the assessment is the result of a signal point assessment carried out by means of the assessment unit 109. If the level of the signal received is one of four points located in the vicinity of an origin, the appreciation result signal goes into a backup state and if this is not the case, it goes into a normal state. This appreciation result signal is used as a signal

backup (5) as is.

  These backup signals instruct each unit to save / cancel the backup of a certain variety of

control parameters.

  Detailed backup conditions and detailed backup cancellation conditions for each backup signal

are as follows.

  Backup signal (1) Backup conditions: when the RT signal is activated and

  a carrier pseudo-detection signal is cut.

  Backup cancellation conditions: when a signal from

  Carrier pseudo-detection is activated or the RT signal is cut.

Backup signal (2)

  Backup conditions: when a pseudo signal

carrier detection is cut.

  Backup cancellation conditions: when either the 2.5 second counter 142 or the 15 second counter 143 is activated. Backup signal (3) Backup conditions: when the RT signal is activated and

  a carrier pseudo-detection signal is cut.

  Backup cancellation conditions: when either the counter at 2.5 seconds 142 or the counter at 15 seconds 143 is

  activated or when the RT signal is cut off.

Backup signal (4)

  Backup conditions: when a pseudo signal

carrier detection is cut.

  Backup cancellation conditions: when a pseudodetection carrier signal is activated or when the counter at 15

seconds 143 is activated.

  Backup signal (5) Backup conditions: when the result of the assessment

  is one of four points near an origin.

  Backup cancellation conditions: when the result of the assessment is not one of four points near an origin where the state of only the backup signal (5) changes independently of the state of the carrier (pseudo-detection signal

carrier).

  Then the timing etc. of the change of state of each backup signal shown in FIG. 8 is described using timing diagrams. In the timing diagrams which

  follow, the RT signal is assumed to be always on.

  FIG. 10 is the timing diagram which represents a case in which the carrier cut-off period is shorter than

the time limit allowed.

  In this case, when the carrier is interrupted, the received data becomes abnormal and the carrier pseudo-detection signal becomes cut after the internal delay time in the modem has elapsed. When the carrier pseudo-detection signal becomes cut, all of the backup signals (1) to (4) change from a normal state to a backup state and the parameters of the variety of parameters in the modem are saved. Since the result of the assessment is centered in the vicinity of an origin when the carrier is interrupted, the save signal (5) goes to the state

backup.

  The line at the bottom of the figure represents the data received by the modem. The received data has no relation to the carrier pseudo-detection signal and it becomes abnormal immediately after the carrier is interrupted, i.e. the data cannot be received from the modem from the opposite station. When the carrier is restored before the time limit (15 seconds in this case) has elapsed, the carrier pseudo-detection signal becomes active after the internal delay time of the modem has elapsed. Then the backup signals (1)

  and (4) simultaneously go from the backup state to the normal state.

  When the carrier pseudo-detection signal becomes activated, the 2.5-second counter 142 starts its counting and the backup signals (2) and (3) pass from a backup state to a normal state 2, 5 seconds (as shown as "a while" in Figure 10) after the carrier pseudo-detection signal becomes activated. So receiving data is

  simultaneously restored to the normal state.

  Each unit to be controlled by means of each of the backup signals (1) or (4) cancels the backup and starts a “hooking” (updating of the control parameters) immediately after the carrier has become activated as described above. before. However, a certain amount of time is consumed for the "snapping" to be completed (so that the fluctuations of the parameters are reduced). During the "2.5 seconds" as described above, a time necessary for this "hooking" to be completed is established. Then the saving of each unit to be controlled by means of the saving signals (2) and (3) is canceled after the "hanging" is finished, and thus, a reduction

  Quick parameter fluctuations can be obtained.

  FIG. 11 represents a case in which the period of

  carrier break is longer than the time limit.

  The operation in the case where the carrier is interrupted is the same as that in the case shown in Figure 10. When the time limit (15 seconds) has elapsed, the save signals (2) to (4) pass in the normal state. That is to say, in this case, the backup signals (2) to (4) pass from a backup state to the normal state only after the time limit set by a timer to 15 seconds independently signal status

carrier pseudo-detection.

  When the carrier is restored, the carrier pseudo-detection signal becomes activated after the internal delay time has elapsed. Then simultaneously, the backup signal (1) goes from the backup state to the normal state. After the pseudo-detection signal

  carrier becomes activated, "hooking" of the PLL RT 112, that is

  say the initial synchronization establishment operation with these received signals is restarted. After "hanging" is complete,

  normal data may be received.

  In order to summarize the operation shown in FIGS. 10 and 11, when the carrier cut-off period is long, a new operation for establishing synchronization with signals received from the modem is necessary. In this case, in the example of FIG. 8, it is desirable to cancel the saving and to zero the parameters of the variety of parameters 15 seconds after the signal of pseudo-detection of carrier becomes activated. When the carrier is restored after a short time, the initial synchronization establishment operation is not performed and the backup is canceled for a certain time (2.5 seconds in the example

  in Figure 6) after the carrier has been restored.

  In the case of FIG. 11, since the signal of pseudo-

  carrier detection becomes activated after the time limit (15 seconds) has elapsed, the "hooking" of the PLL RT 112 is carried out

  after the carrier pseudo-detection signal becomes activated.

  Therefore, in this case, the 2.5-second counter 142 does not

does not work.

  However, even when the carrier is restored after the time limit has elapsed, the 2.5-second counter can also be activated when the backup is canceled if necessary. FIG. 12 shows the configuration of a momentary interrupt processing unit 14c in the modem which constitutes a third preferred embodiment of the present

invention.

  Differences in configuration between modems

  shown in Figure 12 and Figure 8 are as follows.

  (1) On the counter at 2.5 seconds 142, the counter output

at 15 seconds 143 is entered.

  (2) The backup signal (2) is the counter output at 2.5 seconds. (3) The backup signal (3) is the output of the logic product unit 146 on which both the RT signal and the 2.5 second counter output 142 which is the backup signal (2) are entered. According to such a configuration, in the momentary interruption processing unit 114c shown in FIG. 12, the backup signals (2) and (3) both always go into the backup cancellation state 2,5 seconds after leaving the

  counter at 15 seconds 143 becomes activated.

  Figures 13 and 14 are timing diagrams which show the output waveform of each unit in the

  momentary interrupt processing 114c shown in FIG. 12.

  The backup signal (5) shown in Figure 12 is omitted from

Figures 13 and 14.

  FIG. 13 represents a case in which the carrier cut-off period is less than 15 seconds, which is the time limit allowed. In FIG. 13, when the carrier is interrupted, the carrier pseudo-detection signal becomes cut off after the internal delay time has elapsed. Then the outputs of the counter at 15 seconds 143 and of the counter at 2.5 seconds 142 both become cut off simultaneously. The 15-second counter 143 starts counting. The backup signals (1) to (4) go into the backup state. Data received becomes normal

  simultaneously with the interruption of the carrier.

  If the carrier is restored before the 15 seconds have elapsed, the carrier pseudo-detection signal becomes activated after the internal delay time has elapsed. Simultaneously with this, the counter output at 15 seconds 143 becomes activated even before

the flow of 15 seconds.

  When the carrier pseudo-detection signal becomes activated, the backup signal (1) goes into a normal state (only when the RT signal is activated. When the RT signal is cut, this signal is always in a normal state regardless of existence / non-existence of the carrier). When the 15-second counter output 143 becomes activated before 15 seconds have elapsed, the save signal (4) changes from a save state to

the normal state.

  When the 15-second counter output 143 becomes activated, the 2.5-second counter 142 starts counting. After 2.5 seconds have elapsed, the backup signal (2) changes from the backup state to the normal state. When the RT signal is activated, the backup signal (3) also changes from the backup state to the normal state at this time. Like the backup signal (1), when the RT signal is cut, the backup signal (3) keeps

still in normal condition.

  When the saving of the parameters of each unit is canceled (when the 2.5-second counter 142 is activated), the

  data reception becomes normal.

  Figure 14 is a timing diagram showing a case in which the carrier cut-off period exceeds 15 seconds, which is the time limit allowed. Since the operation at the time of a carrier interruption is the same as that

  shown in Figure 13, it is not described here.

  When 15 seconds have passed before the carrier is restored, the 15 second counter output 143 becomes activated. Consequently, the backup signal (4) changes from the backup state to the normal state. The 2.5-second counter 142 starts

its counting.

  When an additional 2.5 seconds have passed, the 2.5-second counter output 142 becomes activated. For this reason, the backup signals (2) and (3) both pass from the state

backup to normal state.

  When more time elapses and the carrier is restored, the carrier pseudo-detection signal becomes activated after the internal delay time has elapsed. For this reason, the

  backup signal (1) goes from the backup state to the normal state.

  In addition, when the carrier pseudo-detection signal becomes activated, the "hooking" of the PLL RT 112 is restarted. After "snapping" ends, data can be received normally. In this way, in the momentary interruption processing unit 114c described with reference to FIGS. 12 to 14, the backup signals (2) and (3) always pass from the backup state to the normal state after counting by the counter at 2.5 seconds 142 ends. In this example, a time difference can be established in this timing for the cancellation of the backup in

according to the targets to be ordered.

  It goes without saying that the time limit of 15 seconds and the delay time of 2.5 seconds can be changed appropriately depending on both the environment in which the device is used and a time necessary for "hanging" each unit. For the delay time, two or more values can also

be established if necessary.

  Although, in Figures 8 and 11, five save signals are used, only some of them can be used and the rest may not be used. According to one variant, another

  In addition, a backup signal type can also be established.

  For example, among the backup signals (1) to (5) shown in Figure 8, only the backup signal (2) can be used. Alternatively, only the combination of signals

  backup (1) and (3) can be used.

  Likewise, in FIG. 12, only the combination of the backup signals (1) and (2) can also be used. According to

  a variant, only the backup signal (3) can be used.

  Since, in this way, a plurality of backup signals are established and the conditions for saving / canceling the backup are changed for each saving signal, it follows that the conditions for saving / canceling the saving a certain variety of parameters can be changed. To be more specific, the conditions for saving / canceling the backup can be modified according to the passage of time after the restoration of the carrier.

  or according to the targets to be ordered.

  In accordance with the present invention, when the carrier is restored within the time limit set, the backup is canceled a prescribed time after the restoration of the carrier while when the time limit allocated has elapsed before the restoration of the carrier,

  the backup is canceled simultaneously with the carrier restoration.

* In a conventional device, even if the carrier is restored in the

  time limit, backup is quickly canceled.

  However, in this case, since a "new latching" is not carried out in order to establish synchronization, the timing cannot be adapted and thus, synchronization cannot be obtained. For

  for this reason, there is a risk that a data error will occur.

  However, according to the present invention, since the backup is configured to be canceled after the expiration of a prescribed time, the

  risk of such data error occurring is reduced.

  According to another aspect of the present invention, the backup is canceled immediately after the restoration of the carrier as a function of the targets to be controlled or a prescribed time after the restoration of the carrier. Typically, backups of command targets are canceled simultaneously. Therefore, in this case, depending on the control targets, synchronization may not be possible after the carrier is restored. However, in accordance with this aspect of this

  invention, such a risk is reduced.

  According to another aspect of the present invention, since the saving / canceling of the saving of each control parameter is carried out independently, the saving of parameters at which a deviation will be generated at the time of a short interruption can be canceled immediately after the end of the interruption and the saving of the other parameters can be canceled after the device is synchronized using the signals received from the opposite station at an optimum level, and the saving is delayed until synchronization is complete. In this way, a safe and rapid restoration can be carried out against a

momentary line interruption.

Claims (11)

  1. Apparatus for transmitting and receiving data (20) via a communication network (13), characterized in that it comprises: an output means for outputting a plurality of backup signals to request in instruction a backup / cancellation of a backup of a plurality of parameters related to an operation for receiving data transmitted via the communication network; detection means (113) for detecting an existence / non-existence of signals transmitted via the communication network (13); backup setting means for saving the parameters according to instructions of said backup signals when said detection means (113) detects non-existence of the signals; and backup canceling setting means for canceling saving of the parameters in order according to the instructions of said backup signals when said detecting means (113) detects an existence of the signals after said   detection means detects the non-existence of the signals.   2. Apparatus according to claim 1, characterized in that said backup cancellation establishment means cancels the saving of the parameters in an order different from the order established when said detection means (113) detects the existence of the signals before the expiration of a prescribed time in accordance with the instructions of the plurality of said backup signals when said detection means continues to detect the non-existence of the signals after the expiration of the prescribed time.   3. Method for processing a momentary line interruption in an apparatus for transmitting and receiving data via a communication network, characterized in that it comprises the steps of: detection of an existence / not existence of signals transmitted via the communication network; saving a plurality of parameters related to an operation for receiving data transmitted via the communication network when a non-existence of the signals is detected; and canceling a backup of said plurality of backup signals in order when an existence of the signals is newly detected after the non-existence of the signals is detected. 4. Method according to claim 3, characterized in that the step of canceling the backup cancels the backup in an order different from the established order when the existence of the signals is detected before the expiration of a prescribed time when a detection of the non-existence of the signals continues after the expiration of the prescribed time. 5. Apparatus for transmitting and receiving data (20) via a communication network (13), said apparatus comprising backup signals for requesting in instruction a backup of parameters related to a data reception operation by the intermediary of the communication network, characterized in that it comprises: means for generating a carrier pseudo-detection signal (113) for detecting a carrier for signals transmitted via the communication network and for transmitting as output a detection result as a carrier pseudo-detection signal; a first counter (142 Figure 8) for starting a count in accordance with the carrier pseudo-detection signal and for detecting the flow of a first time; a second counter (143) for starting a count in accordance with the carrier pseudo-detection signal and for detecting the passage of a second time longer than the first time; first backup signal generating means for generating a first backup signal from a logical sum (144) of detection results of the first counter (142) and the second counter (143); a second backup signal generation means for   generate a second backup signal from the pseudo signal   carrier detection; third backup signal generation means for generating a third backup signal from the first backup signal; and fourth backup signal generation means for generating a fourth backup signal from a logical sum (145) of detection results of the pseudo-detection signal   carrier and the second counter (143).   6. Apparatus for transmitting and receiving data (20) via a communication network (13), said apparatus comprising backup signals for requesting in instruction a saving of parameters related to a data reception operation by the intermediary of the communication network, characterized in that it comprises: means for generating a carrier pseudo-detection signal (113) for detecting a carrier for signals transmitted via the communication network and for transmitting as output a detection result as a carrier pseudo-detection signal; a first counter (143 Figure 12) for starting a count in accordance with the carrier pseudo-detection signal and for detecting a flow of a first time; a second counter (142) for starting a count in accordance with the detection result of the first counter (143), for detecting the passage of a second time and for generating a first save signal from the detection result; a second backup signal generation means for   generate a second backup signal from the pseudo signal   carrier detection; third backup signal generation means for generating a third backup signal from the first backup signal; and fourth backup signal generation means for generating a fourth backup signal from a logical sum (145) of an output of the carrier pseudo-detection signal   (113) and the detection result of the first counter (143).   7. Apparatus for transmitting and receiving data (20) via a communication network (13), said apparatus comprising backup signals for requesting in instruction a backup of parameters related to a data reception operation by the communication network intermediary, characterized in that it comprises: a first backup signal generation means for detecting a carrier for signals transmitted via the communication network, for starting a count in accordance with a result detection and to generate a first backup signal whose instructions are modified after the expiration of a first time; and second backup signal generating means for detecting the carrier for the signals, for starting a count according to the detection result and for generating a second backup signal whose instructions are changed after   the flow of a second time longer than the first time.   8. Apparatus for transmitting and receiving data (20) via a communication network (13), said apparatus comprising backup signals for requesting in instruction a backup of parameters related to a data reception operation by the intermediary of the communication network, characterized in that it comprises: a detection means (142, 143) for detecting the lapse of a prescribed time after the transmission of data via the communication network; and instruction modifying means for modifying instructions regarding a saving of the parameters by means of the saving signals in accordance with a detection result of said detection means.   9. Method for processing a momentary line interruption in an apparatus for transmitting and receiving data via a communication network, characterized in that it comprises the steps of: detection of an existence / a non-existence of a carrier for signals transmitted via the communication network; generation of a first backup signal to request in instruction the cancellation of a backup of parameters related to an operation of reception of data transmitted via the communication network when a carrier is detected; and generation of a second backup signal to request in instruction the cancellation of the saving of the parameters related to the operation of receiving data via the communication network, which is different from the first backup signal, a   prescribed time after the carrier is detected.   10. Apparatus for transmitting and receiving data (20) via a communication network (13), said apparatus comprising backup signals for requesting in instruction a saving of parameters related to a data reception operation by the intermediary of the communication network, characterized in that it comprises: means for generating a first backup signal when data transmitted via the communication network are detected; and means for generating a second save signal for requesting instruction to save the parameters, which has a timing different from that of an instruction resulting from the first save signal and is different from the first save signal. 11. Method for processing a momentary line interruption in an apparatus for transmitting and receiving data via a communication network, characterized in that it comprises the steps of: detection of an existence / a non-existence of a carrier for signals transmitted via the communication network; request in instruction for the cancellation of a saving of parameters related to an operation for receiving data transmitted via the communication network a second subsequent time after an existence of the carrier is detected when the existence of the carrier is detected before the expiration of a first time after the non-existence of the carrier is detected; and requests in instruction for the cancellation of a saving of the parameters related to the operation of reception of the data transmitted via the communication network after the expiration of the first time when the existence of the carrier is not detected before the first time has elapsed after the non   carrier existence is detected.