JPH09181757A - Clock supplying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve efficiency and to save labor for maintenance/operation at the time of clock path fault together with the improvement of service cause by the improvement of clock path quality by providing an emergency system slave forced switch control means and a normal system slave forced switch control means. SOLUTION: When emergency system forced control is remotely executed respectively from a station A to a station D, from the station A to a station C and from the station A to a station B in order to detour a clock path along the emergency system (E system) (A → D → C → B station) during recovery work caused by the interruption of transmission line between the stations A and B, the clock slave systems of D, C and B stations are switched from the normal system slave to the emergency system slave, and the clock path preceeds along the emergency system. When normal system forced control is remotely executed from the station A to the station B, from the station A to the station C and from the station A to the station D in order to return the clock path along the normal system (A → B → C → D station) after the recovery of the interruption in the transmission line between the stations A and B, the clock slave systems of stations B and C are switched from the emergency system slave to the normal system slave, and the cloth path proceeds along the normal system.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clock supply device, and more particularly to an STM network (Synchron) in business communication equipment.
ous Transfer Mode; an abbreviation of Synchronous Transfer Mode, which means a synchronous network), relates to a clock supply device installed in each station that constitutes the ous transfer mode.

In recent years, SDH (Synchronous Digital Hierarch; STM) in business communication equipment and self-employed communication equipment
Multiplexing method using a method) The spread of transmission equipment is remarkable. Since the SDH transmission device is provided in the STM network as each station, since the physical transmission line serves as a clock path in the clock dependent synchronous network configuration, various restrictions occur in the configuration of the clock path in the loop transmission line.

In this case, in order to establish a dependent state of clock network synchronization (dependent synchronization configuration) in the STM network, it is necessary to form a star configuration between the upper station and the lower station. This is S
This is because the TM network is a synchronous network and the physical path becomes the clock path as it is.

However, the network configuration cannot always be a star configuration depending on the condition of the transmission line (line), and a loop configuration that can effectively use the transmission line (line) occupies most of the current network.

Therefore, in the clock dependent system switching algorithm of the clock dependent synchronous network, there is a demand for a clock supply device applicable to a loop configuration.

[0005]

2. Description of the Related Art FIG. 7 shows a transition of a clock dependent mode in a loop transmission line of an STM network. In the initial state shown in FIG. 1A, station A is a master station and stations B to D are slave stations. In the loop configuration, the active clock path is station A →
Station B → Station C → Station D in order.

FIG. 8 shows a configuration example of a clock supply device in each slave station, in which a clock receiver 1, a network synchronous oscillator 2, a frequency converter 3, and a clock distributor 4 are cascaded in this order. Further, the clock receiving unit 1 is composed of N system (active system = Normal) and E system (standby system = Emergency) clock receiving (CREC) units 11 and 12, and the network synchronous oscillation unit 2 is the N system and E system. Network synchronous oscillation (PLL) unit 2
1 and 22, the frequency conversion unit 3 is composed of N-system and E-system frequency conversion (PG) units 31 and 32, and
The clock distribution unit 4 distributes N-system and E-system clocks (DI
S) units 41 and 42, and clock distribution units 41 and 4
A clock is supplied from 2 to each synchronizer (not shown).

Further, the clock receivers 11 and 12 commonly supply the output clocks to the network synchronous oscillators 21 and 22, respectively, and the network synchronous oscillators 21 and 22 are also commonly connected to the frequency converters 31 and 32, respectively. ing.

The control unit 5 controls the clock receiving units 11 and 12, the network synchronous oscillating units 21 and 22, and the frequency converting units 31 and 32 to switch between the N system input clock and the E system input clock. doing.

The parts indicated by reference numerals 6 to 9 in the control section 5 are not related to the prior art and are used only in the present invention.

The outline of the function of each unit is as follows. Clock receiving unit 1: Receives an input clock from a higher station, and network synchronization oscillating unit 2
Pass to Since the clock receiving unit 1 is switched (active system → standby system) in response to an input clock disconnection, disconnection information is transferred to the control unit 5.

Network synchronous oscillator 2: Generates a reference clock signal based on the input clock from the clock receiver 1. Here, the input clock and the generated clock are compared in phase, and the phase adjustment control is performed based on the phase difference. The disconnection information is transferred to the control unit 5 in order to perform its own switching (active system → standby system) when the output signal from the network synchronous oscillation unit 2 is disconnected.

Frequency converter 3: Receiving a reference clock signal from the network synchronous oscillator 2 and generating various clock signals in synchronization with the reference clock signal. Self switching for output signal disconnection from the frequency converter 3. In order to perform (active system → standby system), disconnection information is transferred to the control unit 5.

Clock distribution unit 4: Receives various clock signals from the frequency conversion unit 3 and distributes a necessary clock to each network synchronization device.

Control unit 5: Based on the disconnection information from the clock receiving unit 1, switching / returning control suitable for a normal system is performed. Based on the disconnection information from the network synchronous oscillation unit 2, switching / switchback control suitable for the normal system is performed. Based on the disconnection information from the frequency conversion unit 3, switching / returning control suitable for a normal system is performed.

The transition operation of the clock dependent mode of such a clock supply device will be described below with reference to the clock dependent system switching algorithm shown in FIG.

First, the control unit 5 determines whether or not the N-system dependent clock is disconnected based on the disconnection information from the clock receiving unit 11 (step S31). If there is, the N system remains dependent (step S32).

When it is detected in step S31 that the clock is off, this time it is judged whether or not the E-system dependent clock is off based on the disconnection information from the clock receiving section 12 (step S33). When the clock is not interrupted and is normal, the E system is kept dependent (step S34) and the upper system selection is executed (step S35).

In this upper system selection, the clock dependent system is
Prioritize N system selection, E system selection, self-running state,
This is a step for bringing a dependent system to a higher system that is normal.

When it is detected in step S33 that the clock is off, the network synchronous oscillator 2 is controlled to self-run (step S36), and the host system is selected similarly to step S35 (step S37).

The PLL self-running means that the rubidium oscillator inside the clock supply device operates (self-runs) when the active system dependent clock is disconnected and the standby system dependent clock is disconnected.

Table 1 below summarizes the state transitions by such a clock dependent switching algorithm.

[0022]

[Table 1]

[0023]

Now, when the active system dependent clock loss is detected in the B station due to the disconnection of the transmission path between the A station and the B station as shown in FIG. 7 (2), the B station is in the active state. When the system clock is cut off, N → E (active system → standby system) is switched, and an attempt is made to subordinate to station C. However, since the station C is dependent on the station B, the station B and the station C are in a closed loop state as shown in FIG.

In the closed loop state, the master-slave relationship in the slave synchronization configuration disappears, slips occur in the line with other stations, and data errors occur frequently. That is, there is a problem that the service quality (transmission quality) is degraded due to the quality degradation (reliability degradation) of the clock path.

In order to avoid such a closed loop condition, the wiring of the spare system clock input unit of the clock supply system of the station is removed or the spare system clock input unit is not mounted. Can be considered.

However, there is a problem that reliability is deteriorated because the redundant system of the subordinate clock path cannot be taken and the clock path becomes one system. Also, when the closed loop state is brought about, the problem is that the maintenance and operation load is heavy because it is necessary to enter the station and perform the work in order to change the clock path.

Therefore, in order to improve the quality of the subordinate synchronous network configuration and reduce the load of maintenance work in the loop configuration of the STM network, there is a need for a clock supply device which can be applied without restriction to the loop configuration of the STM network. Become.

Further, in order to reduce the load and speed up the maintenance work, it is necessary to have a system capable of automatically switching the subordinate system of the clock supply device when the transmission line of the STM network fails.

Therefore, the present invention is provided in a slave station in a loop-shaped transmission line of an STM network, and when a transmission line failure is detected, a clock path is provided to the master station from the active system subordinate to the standby system subordinate and the standby system subordinate to the active system. In a clock supply device that can switch to a subordinate, by establishing a switching algorithm that can be applied to a loop structure as well as a star structure of an STM network, the quality of the clock path is improved to improve service quality (transmission quality) and a clock path failure. The purpose is to ensure efficiency and labor saving in maintenance and operation at the time.

[0030]

FIG. 1 is an explanatory view of the principle common to the clock supply devices according to the present invention (1) to (3) for achieving the above-mentioned object. Station A is a master station, Station B-D
The state transition of the clock dependent system in the case where the station is the slave station and the loop configuration of the stations A to B, C to D is described. Note that the working system (N system) clock path in the initial state is around A station → B station → C station → D station, as in FIG. 7 (1). Further, here, as in (2) of the same figure, the state transition of the clock path and the detouring means of the clock path when the transmission path disconnection between the A station and the B station occurs will be described.

As described above, when the transmission line disconnection between the A station and the B station occurs, the B station enters the N-system dependent clock disconnection state, so that the internal oscillator (PLL) transits to the free-running state. Station C,
Since there is no state transition of station D, station C is subordinate to station B in the free-running state, and station D is subordinate to station C.

Next, during the recovery work of the transmission line disconnection between the A station and the B station, the clock path is set to the standby system (E system) (A station → D station → C).
To make a detour around station B → station B, station A to station D, A
If the standby system compulsory control is remotely performed from the station to the C station and from the A station to the B station, the clock dependent systems of the D station, the C station, and the B station are switched from the active system dependent to the standby system dependent.
As shown in (3) of the figure, the clock path is around the backup system.

After restoration of the transmission line disconnection between the A station and the B station, in order to restore the clock path around the active system (A station → B station → C station → D station), the A station to the B station and the A station to the C station. Station, station A to D
If the active system forced control is remotely performed on the station, station B,
The clock subordinate system of station C and station D is switched from the subordinate system subordinate system to the subordinate system subordinate system, and the clock paths are around the active system as shown in FIG.

Next, the present inventions (1) to (1) commonly shown in FIG.
Each of the clock supply devices (3) will be described with reference to FIGS. Similar to FIG. 9, these FIGS. 2 to 4 show the outline of the operation of the clock supply device shown in FIG. 8, and only the characteristic parts of the present invention are shown by thick lines. However, in the present invention, as shown in FIG. 8, the control unit 5 is provided with a backup system forced switching control push button 6, an active system forced switching control push button 7, a selection switch 8 and an automatic switching selection switch 9. ing. In addition, for the forced switching control of the active system and the standby system, the switching selection, and the automatic switching selection, the earth remote control may be used instead of the push buttons 6 to 9.

[1] In the present invention (1) which is shown in principle in FIG. 2, a standby system dependent forced switching control means and a working system dependent forced switching control means are provided, and when the working system is dependent, the clock of the working system dependent clock is provided. When the disconnection is detected, the self-running clock state is set, the standby system dependent forced switching control means switches from the self-running state to the standby system dependent clock, and when the standby system is dependent, the self-running clock is detected. A running clock state is set, and the active system dependent forced switching control means switches from the free running state to the working system dependent clock.

That is, in FIG. 2, first, the control unit 5
Is currently dependent on the active system by the push button 7 or the like (step S1), it is determined whether or not the standby system forced control setting means (the push button 6 in FIG. 8) is performing the standby system forced control. If it is "NO" (step S2), it is further determined based on the disconnection information from the clock receiving unit 11 whether or not the active subordinate clock is disconnected (step S3), and the clock is disconnected. If it is normal, the active system remains dependent (step S).
4), when it is detected that the clock is off, as shown in FIG. 1B, the network synchronous oscillator 2 is controlled and self-propelled (step S5).

Since there is no state transition of stations C and D,
Station C is subordinate to station B in the free-running state, and station D is subordinate to station C.

If "YES" in the step S2, it is currently dependent on the backup system (step S2).
6), active system forced control setting means (push button 7 in FIG. 8)
Determines whether or not the active system forced control is being applied (that is, whether or not restoration is confirmed) (step S7). If "YES", the process returns to step S1, but "NO". 1 further determines, based on the disconnection information from the clock receiving unit 12, whether or not the standby system dependent clock is disconnected (step S8). As shown in (), the standby system is made dependent (step S9), but when it is detected that the clock is off, the network synchronous oscillator 2 is controlled and self-propelled (step S10).

That is, during the recovery work of the transmission line clock disconnection between the stations A and B, the clock path is routed around the backup system (station A →
To make a detour from station D → station C → station B), station A to station D,
Step S from station A to station C and from station A to station B
If the standby system compulsory control shown in 2 is executed, station D, station C, station B
The clock subsystem of the station is switched from the active subsystem to the standby subsystem, and the clock path is around the standby subsystem.

After the transmission line clock disconnection between the A station and the B station is recovered, the clock path is changed to the working system (A station → B station → C station → D).
Station) to return to station A to station B, A to C
If the active system compulsory control shown in step S7 is executed from the station A and the station A to the station D, the clock subordinate systems of the stations B, C, and D are subordinate to the standby system as shown in FIG. 1 (4). Is switched to the active system dependent, and the clock path is around the active system.

In this way, when the active system is out of clock, it automatically enters the free-running clock state. From this state,
If the standby system forced switching control is executed, the clock of the station is rotated in the opposite direction (from the active system to the standby system). Therefore, S
It is possible to apply in the loop configuration of the TM network, and it is possible to improve the service quality (transmission quality) by improving the quality of the clock path and to ensure the efficiency and labor saving of the maintenance and operation when the clock path fails. .

The state transitions by the clock dependent switching algorithm are as shown in Table 2 below.

[0043]

[Table 2]

[2] In the present invention (2) shown in principle in FIG. 3, in the clock dependent system switching algorithm, the first switching from the active system dependent clock to the standby system dependent clock or the active system dependent clock. To a free-running clock state from the second to the self-running clock state, and when the first switching is selected by the selecting means, when the clock loss of the active subordinate clock is detected, It is characterized in that the running clock state is held, and when the clock break of the active system dependent clock is detected when the second switching is selected, the standby system dependent clock is switched to.

That is, in FIG. 3, first, the control unit 5
Determines whether or not the active-system dependent clock is currently in the normal or clock-off state (step S11), and when normal, determines that the clock-dependent system is the active-system dependent clock (step S12). The standby system forced control setting means determines whether or not the standby system forced control is being applied (step S13). If "NO", the normal loop returning to step S11 is repeated.

When it is found in step S11 that the active system subordinate clock is in a disconnected state, it is determined whether the selection means (selection selection switch 8 in FIG. 8) is selected as the first switching or the second switching. (Step S1
4) When the first switching, that is, the switching from the active system dependent clock to the standby system dependent clock is selected (N →
E; NOR) further determines whether or not the standby system dependent clock is disconnected based on the disconnection information from the clock receiving unit 11 (step S15). When the clock is not disconnected, it is normal. , The backup system remains as a slave (step S16), and the upper system is selected in the same manner as steps S35 and S37 of FIG. 9 (step S17).

At the time of applying a loop configuration in which the selection means selects the second switching, that is, the switching from the active system dependent clock to the free-running clock state in step S14 (N →
As shown in FIG. 1 (2), the network synchronous oscillation unit 2 is controlled to self-run (INH) (step S18).

At this time, since there is no state transition of stations C and D, station C is subordinate to station B in the free-running state, and station D is subordinate to station C.

Then, the standby system forced control setting means determines whether or not the standby system forced control is being applied (step S19), and if "NO", the upper system is selected (step S20).

That is, during the recovery work of the transmission line clock disconnection between the stations A and B, the clock path is routed around the backup system (station A → D).
Station → station C → station B), so from station A to station D,
Steps S19 from station A to station C and from station A to station B
If the standby system selection remote control shown in Fig. 1 is carried out, the clock dependent system of the D station, C station, and B station is switched from the active system dependent to the standby system dependent as shown in Fig. 1 (3), and the clock path is around the standby system. Becomes

After the recovery of the transmission line clock loss between the stations A and B, the clock path is returned to the working system (station A → station B → station C → station D). Station to C
If the upper selection control in steps S17 and S20 is performed from the station A and the station A to the station D, the clock subordinate systems of the stations B, C, and D are not dependent on the standby system as shown in FIG. 1 (4). It switches to the active system subordination, and the clock path is around the active system.

Further, when the result is "YES" in steps S13 and S20, the backup system forced control is performed by the backup system forced control setting means, so the process returns to step S15 to switch to the backup system dependent clock.

The above-mentioned selection means is a selection switch for application in the star configuration and for application in the loop configuration. NOR selection is applied when the star configuration is applied and INH selection is applied when the loop configuration is applied.

As described above, in the present invention, INH selection (N →
In the case of (self), when the active system dependent clock is cut off due to the transmission line clock cut or the like, the clock of each station automatically becomes the free running clock state. If the standby system dependent forced control is executed from this state, the clocks of the respective stations rotate in opposite directions (around the active system → around the standby system) as shown in FIG. 7C. Note that the standby system dependent forced control is forcibly fixed to the standby system dependent, regardless of whether the current clock dependent system is the active system dependent or the free-running clock state.

Therefore, the application in the loop structure of the STM network becomes possible. In addition, by setting the clock receiver automatic selection switch to NOR selection, N →
E The automatic switching function is enabled, and the conventional star configuration can be applied. The state transitions by the clock dependent switching algorithm are as shown in Table 3 below.

[0056]

[Table 3]

[3] In the present invention (3) which is shown in principle in FIG. 4, the clock dependent system switching algorithm selects whether or not automatic switching from the active system dependent clock to the standby system dependent clock is performed. The present invention is characterized in that it has means, and when the automatic switching is not carried out by the selecting means, when a clock break of the active system dependent clock is detected, it is left as it is and the state is automatically shifted to the free-running clock state.

That is, in FIG. 4, first, the control unit 5
Determines whether or not the active-system dependent clock is currently in the normal or clock-off state (step S21), and when normal, determines that the clock-dependent system is the active-system dependent clock (step S22). The standby system forced control setting means determines whether or not the standby system forced control is applied (step S23). If "NO", the normal loop returning to step S11 is repeated.

When it is found in step S21 that the active system dependent clock is in the disconnected state, the selecting means (automatic changeover selection switch 9 in FIG. 8) automatically determines from the active system dependent clock to the standby system dependent clock in step S24. When it is determined that the switching is selected (with the automatic switching from N to E), it is further determined based on the disconnection information from the clock receiving unit 11 whether or not the standby system dependent clock is disconnected. (Step S25) If the clock is not interrupted and is normal, the standby system is kept dependent (Step S26), and Step S3 of FIG.
5, the upper system is selected similarly to S37 (step S2).
7).

In this case, since there is no state transition between the C station and the D station, the C station is subordinate to the B station in the free-running state, and the D station is subordinate to the C station.

When it is found in step S25 that the standby system dependent clock is in the disconnected state, the process shown in FIG.
As shown in, the network synchronous oscillator 2 is controlled and self-propelled (step S28). Then, the upper system is selected (step S29).

When the selecting means does not select the automatic switching from the active system dependent clock to the standby system dependent clock in step S24 (when the loop configuration is applied), the process proceeds to step S22 and the active system dependent clock is left as it is. .

Therefore, if this state is maintained, the network-synchronous oscillator 2 will naturally run as shown in FIG. 1 (2).

As described above, during the recovery work of the transmission line clock disconnection between the A station and the B station, the clock path is set to the standby system (A station → D station).
Station → station C → station B) to detour around station A to station D
If the N → E system compulsory switching control shown in step S24 is executed for the station A, station A to station C, and station A to station B, D
The clock dependent system of the station, the C station, and the B station is switched from the active system dependent system to the standby system dependent system, and the clock path is around the standby system as shown in FIG. 1 (3).

After the recovery of the transmission line clock interruption between the A station and the B station, the clock path is changed to the active system (A station → B station → C station → D).
Station) to return to station A to station B, A to C
If the upper selection control shown in steps S27 and S29 is performed from the station A and the station A to the station D, the clock dependent systems of the stations B, C, and D are switched from the standby system dependent to the active system dependent. As shown in 1 (4), the clock path is around the active system.

As described above, according to the present invention, when the active system dependent clock is disconnected due to the transmission line clock disconnection or the like, the clock of each station becomes a free-running state, so that the current state of the clock dependent system is the active system dependent. Even if it is self-propelled, it will be forcibly fixed to the subordinate system.

From this state, if the N → E (remote) switching control is executed, the clocks of the respective stations will be in opposite directions (around the active system → around the standby system) as shown in FIG. 7 (3). Therefore, S
It can be applied in the loop configuration of the TM network. It should be noted that the star configuration is used when N → E (remote) switching control is not executed (N
OR).

Further, by setting the clock input section automatic changeover selection switch to NOR selection, the N of the clock input section is selected.
→ E The automatic switching function will be enabled, and the conventional star configuration can be applied.

The state transitions by the clock dependent switching algorithm are as shown in Table 4 below.

[0070]

[Table 4]

[4] In the above-mentioned present inventions (1) to (3), the switching trigger signal detected by the STM transmission device is passed through the alarm transfer device and the standby system compulsory control terminal of the clock supply device of the own station. Further, the switching trigger signal can be sent to the STM transmission device of the lower station via the alarm transfer device.

As a result, when the dependent clock is around the upper station when the transmission path clock on the upper station side is cut off, etc., the dependent clock selection system of the local station clock supply apparatus and the dependent clock of the lower station clock supply apparatus. It is possible to automatically switch the selected system (active system dependent → standby system dependent). This makes it possible to automatically switch the subordinate clock selection system of stations in the same loop. If the subordinate clock is in the lower station, the current state is held because it works as a suppression control.

Further, the switching trigger signal from the opposite direction (lower station side) is input to the active system forced control terminal of the clock supply device of the own station via the alarm transfer device, and the switching trigger signal is also alarmed. It can be sent to the STM transmission device of the upper station via the transfer device.

As a result, when the subordinate clock is in the vicinity of the subordinate station when the transmission path clock on the subordinate station side is cut off, etc., the subordinate clock selection system of the own station clock supply device and the subordinate clock of the clock supply device of the upper station. It is possible to automatically switch the selected system (standby system dependent → active system dependent). This makes it possible to automatically switch the subordinate clock selection system of stations in the same loop. Also, when the dependent clock is around the upper station, the current state is held because it works as a suppression control.

In this way, the present invention is used in combination with a device capable of transferring the switching trigger information of the transmission device, and has a configuration in which the subordinate system of the clock supply device can be automatically switched when the transmission line fails. It is possible to improve the efficiency of maintenance and operation in the event of a failure and to save labor.

[0076]

5 and 6 show an embodiment of a loop transmission line using a clock supply device according to the present invention. In the configuration example shown in FIG. An example of a station (both slave stations) is shown in FIG. 5, and an example of a station A (master station) and a station D (slave station) is shown in FIG.

5 and 6, a is an STM transmission device, b is an alarm transfer device, and c is a clock supply device.
Further, the DCC is a DCC (Data C in the SDH transmission frame.
This indicates an empty byte such as an Ommunication Channel byte and is used to transfer the AT1 by superimposing it on the main signal. AT1 indicates a switching trigger signal that is issued when a transmission line clock loss is detected or when the device fails. Also, CSEND
Is a clock transmission unit of the STM transmission device, and CREC is a clock reception unit (see FIG. 8) of the clock supply device.

Here, the switching trigger signal AT1 detected by the STM transmission device a is configured to be input to the standby system compulsory control terminal of the clock supply device c of the own station via the alarm transfer device b. Further, the switching trigger signal AT1 is input to the empty byte of the STM transmission device a for the lower station via the alarm transfer device b in order to transfer it to the lower station.

The alarm transfer device b performs signal branching to input the switching trigger signal AT1 to both the standby system compulsory control terminal of the local station clock supply device c and the empty byte of the SDH transmission device for lower stations. .

Further, the switching trigger signal AT1 transferred from the upper station in an empty byte is inputted to the standby system compulsory control terminal of the own station clock supply device c via the alarm transfer device b.

With the above configuration, when the subordinate clock is in the vicinity of the upper station when the transmission path clock on the upper station side is cut off, etc., the subordinate clock selection system of the own station clock supplying device c and the clock supplying device c of the lower station. It is possible to automatically switch the subordinate clock selection system of (N subordinate → E subordinate). This makes it possible to automatically switch the subordinate clock selection system of stations in the same loop. Further, when the dependent clock is in the vicinity of the lower station, the current state is held because it works as the inhibition control.

Similarly, the switching trigger signal AT1 from the opposite direction (lower station side) is input to the active system forced control terminal of the clock supply device c of the own station via the alarm transfer device b. There is.

Further, in order to transfer the switching trigger signal AT1 to the upper station, the S for the upper station is sent via the alarm transfer device b.
The TM transmission device a is configured to be input to an empty byte. Note that the alarm transfer device b uses the switching trigger signal A of its own station.
Signal coupling is performed in order to input the switching trigger signal AT1 from T1 and the lower station to the empty byte of the STM transmission device a for the upper station.

With the above configuration, when the subordinate clock is in the vicinity of the subordinate station when the transmission line clock on the subordinate station side is cut off, etc., the subordinate clock selection system of the own station clock supplying device c and the clock supplying device c of the upper station. It becomes possible to automatically switch the dependent clock selection system of (E system dependent → N system dependent). This makes it possible to automatically switch the subordinate clock selection system of stations in the same loop. Also, when the dependent clock is around the upper station, the current state is held because it works as a suppression control.

Next, in the above embodiment, the operation in the case of automatically switching the clock dependent system is as shown in FIG. 1, in which the A station is the master station, the B station, the C station, and the D station are the slave stations. Station A-B
The state transition of the clock dependent system in the case of the loop configuration of the station, the station C, and the station D will be described. The working clock path in the initial state is around A station → B station → C station → D station.
An embodiment in which the clock path is automatically switched when a transmission line clock interruption between the station and the station B occurs will be described with reference to the symbols in the figure.

In this state, when the transmission line clock loss between the stations A and B occurs, the station B detects the transmission line clock loss at the STM transmission device a and generates the switching trigger signal AT1 at the STM transmission device a. To do.

Next, the switching trigger signal AT1 is branched into two by the alarm transfer device b, one of which is the clock supply device c.
Input to the standby system forced control terminal of.

As a result, the clock subordinate system of the station B is automatically switched from the active subordinate system to the standby subordinate system. The other switching trigger signal AT1 is transferred to the C station by the empty byte DCC.

Next, in the C station, the empty byte DC is transmitted from the B station.
The switching trigger signal AT1 transferred by C is branched into two by the alarm transfer device b, one of which is the clock supply device c.
Input to the standby system forced control terminal of. As a result, the clock subordinate system of the station C is automatically switched from the active subordinate system to the standby subordinate system. The other switching trigger signal AT1 is
It is transferred to station D by the empty byte DCC.

In the D station, the switching trigger signal AT1 transferred from the C station by the empty byte DCC is input to the standby system compulsory control terminal of the clock supply device c via the alarm transfer device b. As a result, the clock dependent system of the D station is automatically switched from the active system dependent to the standby system dependent.

Therefore, when the transmission path clock between the A station and the B station is cut off, the clock path is routed around the backup system (A station → D station → C station → D).
Station) can be automatically switched. Also, station A to B
If the subordinate clock is in the standby system (A station → D station → C station → D station) when the station transmission line clock is cut off, the current state is held because it works as a suppression control.

As described above, the operation when the transmission path clock loss between the A station and the B station occurs when the clock path is configured around the working system, the transmission path clock interruption between the B station and the C station has been described. , And the operation is the same when the transmission line clock between the C station and the D station is disconnected. Also, the operation when the clock path is configured around the backup system can be considered in the same manner.

[0093]

According to the present invention, it is possible to apply the clock supply system which can be applied not only to the star structure of the STM network but also to the loop structure. Further, by using it in combination with the alarm transfer device capable of transferring the switching trigger information of the STM transmission device, it becomes possible to automatically switch the clock subordinate system of the clock supply device when the transmission line of the STM network fails.

Therefore, the quality of the subordinate synchronous network configuration in the loop configuration of the STM network is improved and the maintenance work load is reduced,
Furthermore, the quality of service can be improved by the speed of maintenance work.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of a clock supply device according to the present invention (1) to (3).

FIG. 2 is a flowchart showing a clock dependent system switching algorithm of the clock supply device according to the present invention (1).

FIG. 3 is a flowchart showing a clock dependent system switching algorithm of the clock supply device according to the present invention (2).

FIG. 4 is a flowchart showing a clock dependent system switching algorithm of the clock supply device according to the present invention (3).

FIG. 5 is a block diagram (No. 1) showing an embodiment of the clock supply device according to the present invention (1) to (3).

FIG. 6 is a block diagram (No. 2) showing an embodiment of the clock supply device according to the present invention (1) to (3).

FIG. 7 is a diagram illustrating the principle of a conventional example.

FIG. 8 is a standard block configuration diagram of a clock supply device according to a conventional example and the present invention.

FIG. 9 is a flowchart showing a clock dependent system switching algorithm in a conventional example.

[Explanation of symbols]

 1,11,12 Clock receiver 2,21,22 Network motive oscillator 3,31,32 Frequency converter 4,41,42 Clock distributor a STM transmitter b Alarm transfer device c Clock supplier CSEND Clock transmitter CREC Clock receiver In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (7)

[Claims] 1. A clock path provided in a slave station in a loop-shaped transmission line of an STM network, and switches a clock path from the active system subordinate to the standby system subordinate and the standby system subordinate to the active system subordinate to the master station when a transmission line failure is detected. A possible clock supply device has a standby system dependent forced switching control means and a working system dependent forced switching control means, and when the active system dependent is detected as a free running clock state when a clock break of the working system dependent clock is detected, The system dependent forced switching control means switches from the self-running state to the standby system dependent clock, and when the standby system is dependent, the self-running clock state is set when the clock failure of the standby system dependent clock is detected, and the active system dependent forced switching control means A clock supply device characterized by switching from the self-running state to the active system dependent clock by means of. 2. A clock supply device provided in a slave station in a loop-shaped transmission line of an STM network and capable of switching a clock path from a working subordinate to a standby subordinate to a master station when a transmission line fault is detected. There is provided means for selecting whether the first switching from the active system dependent clock to the standby system dependent clock or the second switching from the active system dependent clock to the free running clock state, and the second switching by the selecting means. Is selected, the free-running clock state is held when a clock loss of the active system dependent clock is detected, and a clock loss of the active system dependent clock is detected when the first switching is selected. A clock supply device characterized by switching to the standby system dependent clock when this occurs. 3. A clock supply device provided in a slave station in a loop-shaped transmission line of an STM network, and capable of switching a clock path from a working subordinate to a standby subordinate to a master station when a transmission line fault is detected. A means for selecting whether or not to automatically switch the active system dependent clock to the standby system dependent clock is provided, and the clock failure of the active system dependent clock is detected by the selecting means when the automatic switching is not performed. When it does, the clock supply device is characterized in that it is left as it is and is naturally shifted to the free-running clock state. 4. The auxiliary system dependent forced switching control means according to claim 2 or 3, wherein the standby system dependent forced switching control means switches from the free-running clock state to the standby system dependent clock. Clock supply device. 5. A clock supply according to any one of claims 1 to 4, wherein when switching to the standby system dependent clock, when the clock failure of the standby system dependent clock is detected, the self-running clock state is set. apparatus. 6. The active system dependent forced switching control means according to claim 1, wherein the active system dependent forced switching control means restores the standby system dependent clock to the active system dependent clock. Clock supply device characterized by. 7. The alarm transfer device according to claim 1, wherein each station comprises an STM transmission device, an alarm transfer device, and a clock supply device, and the switching trigger signal detected by the STM transmission device is sent to the alarm transfer device. Via the alarm input device as a signal for standby system forced control of the clock supply device of the local station, and the switching trigger signal is sent to the STM transmission device of the lower station or the upper station via the alarm transfer device. Clock supply device.