JP3123515B2 - Time synchronization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time synchronization system between a master station and a slave station connected to a network, and more particularly, to an analog voice communication path and a highway (a plurality of stations used in time division switching). The present invention relates to a time synchronization method between a plurality of stations connected by a physical line in which signals are multiplexed.

[0002]

2. Description of the Related Art Conventionally, this type of time synchronization system is disclosed in, for example, Japanese Unexamined Patent Publication No. 3-80797, in which each time is monitored between a monitoring station (master station) and a monitored station (slave station). It is used to synchronize between the master station and the slave station by time correction based on the information difference.

FIG. 4 is a block diagram showing the configuration of a conventional time synchronization system. When the status change information to be transmitted to the monitoring station (master station) 1 occurs in the slave station 2, the status change information transmission circuit 11 is activated, and the clock 7 of the slave station is displayed in the notification time information transmission circuit 8. The time information is added and transmitted to the master station 1. The master station 1 receiving the time information added to the state change information from the slave station 2 transmits the time information to the error circuit 4. The error circuit 4 detects a difference between the time information displayed by the clock 3 of the master station and the time indicated by the time information received from the slave station 2,
The difference information is notified to the comparator 5.

The comparator 5 compares a preset time Δt with the notified difference information, and sends a time correction request signal to the time information transmitting circuit 6 only when the difference is not less than Δt. Send to The time information transmitting circuit 6 having received the time correction request signal transmits the current time displayed on the clock 3 of the master unit to the slave station 2 as a time correction signal in accordance with the time correction request signal. In the slave station 2, when the reception circuit 9 receives the time correction signal, the time correction circuit 10 is activated and corrects the clock 7 of the slave station.

[0005]

However, the above-mentioned method has several problems and has been a problem. The first problem is that if a failure occurs in a master station having a clock serving as a reference, the slave station cannot receive any signal serving as a reference for synchronization. Is not done. The reason is that the master station has entirely determined the reference time and supplied the time information to the slave stations.

A second problem is that the load on the master station increases as the number of slave stations increases in order to synchronize the stations. This is because the master station individually transmits time information and time difference information to a plurality of slave stations in response to a request from the slave station when synchronizing the stations.

The present invention has been made under such a background. Even when a failure occurs in a master station, the slave station performs autonomous operation and synchronizes with a reference signal, thereby compensating time synchronization between the stations. It is an object of the present invention to provide a time synchronization system that can perform the time synchronization.

[0008]

According to the first aspect of the present invention, a monitoring station (master station) and a plurality of monitored stations (slave stations) are used for analog voice communication paths and highways (used in time division switching). In a network system connected by a physical line in which a plurality of signals are multiplexed), the master station is transmitted via an analog voice communication path from a master station built-in clock and a reference signal transmitter serving as a reference for time synchronization. A base station input level measuring circuit for measuring the input level of the reference signal, a level information insertion circuit for sending level information to the slave station based on the measured input level, and a master information input circuit for measuring the input level of the reference signal. A slave station processor that corrects a clock inside the station, wherein the slave station includes a slave station built-in clock, a slave station input level measurement circuit that measures an input level of the reference signal, and the master station via the highway. A level information extracting circuit for extracting the level information sent from the controller, a level difference calculating circuit for calculating a difference between the measured input level of the reference signal and the extracted level information, and transmission by the difference (relative level). A memory storing delay time as data, and a slave processor for correcting the built-in slave clock by adding the transmission delay time data read from the memory to an input level measured by the slave station input level measurement circuit. A time synchronization system is provided.

According to a second aspect of the present invention, the reference signal transmitter is a reference signal transmitted at a preset repetitive transmission cycle, a predetermined voltage, a predetermined audio frequency, and a predetermined transmission duty ratio. A time synchronization method according to claim 1 is provided.

According to a third aspect of the present invention, the level information uses two time slots of the m-th and (m + 1) -th of the highway, and the m-th slot contains a sign of the input level. 3. The time synchronization system according to claim 1, wherein the input level value of the (m + 1) th slot is information accommodated in HEX data.

[0011]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a time synchronization system according to an embodiment of the present invention. In this figure, the system includes a reference signal transmitter 10 for transmitting a reference signal for synchronizing between stations, and a master station 20.
And the slave station 30.

The master station 20 has a built-in clock 23, an input level measuring circuit 21 for measuring the input level of the analog reference signal and judging the input of the reference signal, a processor 22 for correcting the built-in clock 23, and an input level measuring circuit 21. The level information insertion circuit 24 inserts the input level information obtained on the highway 50 with the slave station.

The slave station 30 has a built-in clock 36, an input level measuring circuit 31 for measuring and monitoring the input level of the reference audio signal received via the master station, and input level information sent from the master station 20 on the highway 50. , A level difference calculation circuit 33 for calculating the difference between the input level at the master station 20 and the input level at the own station, and delay information on the transmission time of voice due to transmission loss. The read-only memory 35 determines the input of the reference signal,
And a processor 34 for correcting the internal clock 36 in accordance with the level difference.

The reference signal transmitter 10 constantly transmits a reference signal having a transmission time T at a predetermined repetition transmission period t, a predetermined voltage, and a predetermined voice frequency as shown in FIG. Normally, the repetitive transmission cycle t is 1 to several s
ec, the signal transmission time T is several tens msec to several tens msec.
A signal of 0 msec is used.

In the master station 20, the reference signal is received by the input level measurement circuit 21, the input level of the reference signal is measured, and the level information is output to the level information insertion circuit 24 as HEX data. When the input of the reference signal exceeds the threshold value, the input level measuring circuit 21 determines that there is an input, and notifies the processor 22 of the input. When the processor 22 receives the input confirmation signal of the reference signal from the input level measurement circuit 21, it corrects the built-in clock 23. The level information insertion circuit 24 inserts HEX data into the m-th and m + 1-th time slots (FIG. 3) of the highway for the slave station.

On the other hand, the slave station 30 measures the input level of the reference signal and monitors the input of the reference signal in the input level measuring circuit 31 in the same manner as the master station 20, and outputs the result of measuring the input level to the level difference calculating circuit 33. Next, the processor 34 is notified of the input confirmation signal of the reference signal. Level difference calculation circuit 33
Then, the difference between the level information from the input level measuring circuit 31 and the input level of the master station extracted from the highway by the level information extracting circuit 32 is calculated, and the calculation result is notified to the processor 34.

The read-only memory 35 stores the relationship between the level loss due to the transmission loss and the transmission delay time as data. In the processor 34, the level difference calculation circuit 3
The transmission delay time corresponding to the level difference calculated in step 3 is taken out from the read-only memory, and
The internal clock 36 is corrected by adding it to the reference signal input confirmation signal from 1.

Next, another embodiment of the present invention will be described with reference to FIG. 1 because the configuration is the same as that of the above-described embodiment. In this figure, between the master station and the slave station,
An analog voice communication path and a network system connected by a highway for exchanging signals between stations, wherein a predetermined repetitive transmission cycle t, a predetermined voltage, a predetermined A reference signal transmitter 1 for constantly transmitting a reference signal having a transmission time T at a voice frequency.
0 and a master station 20 and a slave station 30 that require inter-station synchronization.

The master station 20 can advance by a time required for operation (for example, a 60-minute minute counter) and a built-in clock 23 and an analog signal transmitted from the reference signal transmitter 10 and serving as a synchronization reference. An input level measurement circuit 21 for monitoring input level measurement and input of a reference signal, a processor 22 for correcting a built-in clock 23, and input level information measured by the input level measurement circuit 21 as a HEX data to a highway to a slave station. And a level information insertion circuit 24 inserted into the above two specific time slots (for example, time slots m and m + 1).

Similar to the master station 20, the slave station 30 has a built-in clock 36 which can be advanced at a time required for operation.
And an input level measurement circuit 31 received via the master station, a level information extraction circuit 32 for extracting input level information at the master station from a specific time slot on the highway, an input level at the master station and an input level at the own station Level difference calculating circuit 33 for calculating the difference from the analog signal, a read-only memory 35 for storing information on transmission time delay due to transmission loss in the analog voice communication path, and monitoring the input of the reference signal to obtain the calculated relative level. A processor 34 for correcting the built-in clock 36
It is composed of

Next, the operation of this embodiment will be described. The reference signal transmitter 10 constantly transmits a reference signal of a transmission time T at a predetermined transmission frequency and a repetition transmission period t as shown in FIG. Assuming that the reference for inter-station synchronization is the time when an audio frequency is generated and that each station corrects the built-in clock by confirming the input of the reference signal, the synchronization accuracy between the stations can be reduced by shortening the repetition transmission cycle t of the reference signal. Can be improved.

In the master station 20, the reference signal is received by the input level measuring circuit 21, and the input level of the reference signal is measured. The measured level information is output to the level information insertion circuit as HEX data. At the same time,
The input level measurement circuit 21 sets a threshold value of the integrated value of the signal voltage in one repetition transmission cycle as a criterion for determining the input of the reference signal, and determines that there is an input when the integrated value exceeds the threshold value. It notifies the processor 22 as an input confirmation signal.

The processor 22 includes an input level measuring circuit 21
When the input confirmation signal of the reference signal is received from the
Correct 3 The built-in clock 23 is an n-ary counter (where n>
t), and the count value is reset to zero unconditionally by the correction signal from the processor 22. In the level information insertion circuit 24, the positive / negative sign of the input level is assigned to the time slot m, the input level value is assigned to the time slot m + 1, and the HEX data is assigned to the m-th and m + 1-th time slots (FIG. 3) of the highway for the slave station. Insert as

On the other hand, in the slave station 30, the input level measurement circuit 31 measures the input level of the reference signal and determines the input of the reference signal in the same manner as the master station. At this time, the threshold value of the integrated value of the signal voltage for making the input determination is the same as that of the master station 20. The measurement result of the measured input level is sent to the level difference calculation circuit 33, and the input confirmation signal of the reference signal is sent to the processor 34.
Notify.

In the level difference calculation circuit 33, the level information from the input level measurement circuit 31 and the level information extraction circuit 3
In step 2, the difference from the input level of the reference signal at the master station extracted from the highway is calculated, and the calculation result is notified to the processor 34. The difference calculation of the level can be expressed as follows based on the input level at the master station. Relative level (loss level) = input level at master station−input level at slave station Also, assuming that the material used for the analog voice communication path is constant, the time due to voice transmission loss due to the resistance of the material Since the delay has a certain relationship with the loss level, this is stored in the read-only memory 35 as a data table.

In the processor 34, the level difference calculation circuit 3
The transmission delay time corresponding to the relative level (loss level) calculated in Step 3 is taken out from the read-only memory 35 and added to the reference signal input confirmation signal from the input level measurement circuit 31 to correct the built-in clock 36. Do. The built-in clock 36 is also an n-ary counter like the master station, and is reset to zero by a correction instruction from the processor 34. Through the above series of operations, it is possible to synchronize the master station and the slave station.

From the relative level difference with respect to the reference master station, the sound processing means, the calculation means, and the delay time storage means of the slave station determine whether the sound signal is received by the master station apparatus until it is received by the slave station apparatus. Time delay can be predicted,
By correcting the slave clock according to the predicted delay time, time synchronization between stations can be easily performed. Even when a large number of slave stations are connected, the master station simply inserts input level information into specific time slots m and m + 1 by confirming the input of the reference signal, and the slave station extracts level information from the time slots. Therefore, the load on the master station does not increase.

The operation of one embodiment of the present invention has been described above in detail with reference to the drawings. However, the present invention is not limited to this embodiment, and a design change or the like may be made without departing from the gist of the present invention. The present invention is also included in the present invention.

[0029]

As described above, the first effect of the present invention is that the synchronization between slave stations is compensated even if a failure occurs in the master station. The reason for this is that different devices are used to transmit the reference time and the signal that serves as the reference for synchronization between the stations.

The second effect is that the processing load on the master station when synchronizing the stations is reduced. The reason is that when the master station confirms the input of the reference time, it outputs the level information unconditionally, so the transmission of the time information from the slave station, the monitoring of the time information request of the master station, and the transmission of the time information are not required. This is because it becomes unnecessary.

A third effect is that the occupation of time slots used for synchronizing stations is reduced.
The reason is that the time information for each slave station is "hour",
Because it was necessary to send three types of "minute" and "second",
At least three time slots (one byte each for HEX data, three bytes in total) are required for one slave station, and as the number of slave stations increases, the number of time slots used for transmitting time information increases. On the other hand, according to the present invention, regardless of the number of slave stations, the input level is only inserted into the time slot when confirming the input of the reference audio signal, so that only two time slots are occupied as described above. It is.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a time synchronization system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a reference signal used for a time synchronization method according to an embodiment of the present invention.

FIG. 3 is an example of a highway data format used for a time synchronization method according to an embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a time synchronization system according to a conventional technique.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 reference signal transmitter 20 master station 21 input level measurement circuit 22 processor 23 internal clock 24 level information insertion circuit 30 slave station 31 input level measurement circuit 32 level information extraction circuit 33 level difference calculation circuit 35 read-only memory 36 internal clock 40 analog Voice channel 50 Highway

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04J 3/00-3/26 H04L ⁷ /00-7/10 H04L 12/28-12/44 G06G 1/04-1 /14

Claims (3)

(57) [Claims] 1. A monitoring station (master station) and a plurality of monitored stations (slave stations) are connected by an analog voice communication path and a highway (a physical line in which a plurality of signals used in time division switching are multiplexed). The master station comprises: a master station built-in clock; and a master station input level for measuring an input level of a reference signal transmitted via an analog voice communication path from a reference signal transmitter serving as a reference for time synchronization. A measuring circuit; a level information insertion circuit for transmitting level information to the slave station based on the measured input level; and a master station processor for correcting the master station built-in clock based on the input level of the reference signal. A slave station built-in clock; a slave station input level measuring circuit for measuring an input level of the reference signal; and extracting the level information sent from the master station via the highway. A level information extracting circuit, a level difference calculating circuit for calculating a difference between the measured input level of the reference signal and the extracted level information, and a memory storing a transmission delay time based on the difference (relative level) as data. A slave station processor for adding the transmission delay time data read from the memory to the input level measured by the slave station input level measuring circuit to correct the slave station built-in clock. Synchronization system. 2. The apparatus according to claim 1, wherein the reference signal transmitter is a reference signal that transmits at a preset repetition transmission cycle, a predetermined voltage, a predetermined voice frequency, and a predetermined transmission duty ratio. The time synchronization method described. 3. The level information uses the m-th and m + 1-th time slots of the highway, wherein the m-th slot contains the sign of the input level, and the m + 1-th slot contains The input level value is HE
3. The time synchronization method according to claim 1, wherein the information is information contained in X data.