JPH039666B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a line concentration distribution system that handles data by time division.

[Technical background of the invention and its problems]

With the recent trend toward office automation, various electronic devices (facsimile machines, computers, etc.) are being widely used in offices. It is desired to construct a local area network having a data exchange function using terminals including these electronic devices and telephones. Unlike traditional networks using private branch exchanges (PBXs), it is extremely difficult to connect all terminals directly to the PBX.

This difficulty can be alleviated by providing lacal equipment that connects terminals to each area, such as a building or floor. Instead of wiring a transmission line from each such concentrator to a PBX that functions as a central unit,
Connecting each concentrator/distributor to any point on a bus extending from the central unit simplifies the configuration of the local area network. In such a network, signal transmission and reception is performed by time division.

However, the signal transmission time between the central unit and each concentrator/distributor differs depending on the connection position of the concentrator/distributor to the bus, and since signal transmission and reception is performed on a time-sharing basis, the signal transmission time from the concentrator to the central Collisions and extra space may occur between the signals transmitted to the device. It is clear that collisions are unfavorable for signal transmission. Additionally, the excess space reduces signal transmission efficiency.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a line concentration distribution system that is a flexible system that can eliminate the above-mentioned drawbacks and easily eliminate signal collisions on a transmission path.

[Summary of the invention]

The present invention is a system in which a plurality of line concentration and distribution terminals are connected to a pair of transmission lines from a central unit, in which signals destined for the plurality of line concentration and distribution terminals from the central unit are loaded on one transmission line in a time-sharing manner. , signals from multiple terminals to the central device are time-divisionally transmitted on the other transmission path.

For such a system, the present invention transmits a test signal from the central device before transmitting a significant signal, and controls the timing of sending the signal from each terminal to the central device based on the response from the concentration distribution terminal. It is characterized by

More specifically, the test signal has a synchronization signal component determined for each concentration distribution terminal. The delay time between the central device and each line concentration/distribution terminal is measured from the response signal sent back from each line concentration/distribution terminal in response to such a test signal. From this delay time, a control signal for giving the transmission timing from each line concentration/distribution terminal to the central unit is calculated and sent to each line concentration/distribution terminal.

Each line concentration/distribution terminal has means for controlling the timing of sending signals to the central device using this control signal, thereby eliminating signal collisions on the transmission path.

〔Effect of the invention〕

According to the present invention, the delay time is measured using a test signal, and the timing of transmitting the signal from each line concentration/distribution terminal is controlled based on the result, so that signal collisions on the transmission path are eliminated.

Moreover, since the delay time is measured using the test signal, collisions can be eliminated even if the connection state of the line concentration distribution terminal to the transmission path changes. This leads to flexible use of the system.

[Embodiments of the invention]

FIG. 1 shows a network system according to an embodiment of the present invention. It comprises a central unit 11, a plurality of concentrators 12 ₁ to 12 ₄ and at least one terminal 13 connected to each concentrator and distributor. An uplink 14a and a downlink 14b are wired from the central device 11 as a signal transmission path 14, and an output line 15a and an input line 15 of each concentrator/distributor are wired.
b are connected to the uplink 14a and downlink 14b, respectively. Each concentrator/distributor 1
A terminal 13 connected to the terminal 2 is a telephone, a facsimile, or a terminal for a time sharing system. Alternatively, it may be a combination of various terminals.
Furthermore, the signal transmission path may be an optical transmission path.

For convenience of the following explanation, four line concentrators 12
₁ to 12 ₄ It is assumed that it is connected to the central device 11 in the illustrated positional relationship. That is, the line concentration distribution device 1
2 ₁ is connected to the signal transmission line 14 at the position closest to the central unit 11, and the line concentrator/distributor 12 ₄ is connected to the transmission line 14 at the position farthest from the central unit 11. The signal transmission time between the central unit 11 and each concentrator/distributor depends on the location of this concentrator/distributor.

The central device 11 has the function of exchanging data between terminals, and if all the terminals are telephones, it is called a private branch exchange in the usual sense.
exc-change; PBX). Each line concentrator/distributor time-division multiplexes signals from the terminals 13 connected to it, and sends them together with a synchronization signal (including address information for identifying the line concentrator/distributor) to the uplink 14a.
send to. The signals sent out from each line concentrator/distributor in this manner constitute one word. The length of one word depends on the number of terminals connected to each concentrator and distributor. The central unit 11 receives words from each concentrator and distributes and exchanges received data based on subscriber data. The central device 11 further includes:
Words addressed to each concentrator/distributor after data exchange are 1 in the predetermined order assigned to the concentrator/distributor.
It is transmitted to the downlink 14b in a time-division manner within the frame time. The time length of one frame depends on the number of line concentrators and terminals.

Each concentrator receives the word addressed to it identified by the word synchronization signal and distributes the received data to the corresponding terminal. The line concentrator/distributor is
It is configured to send a new word from the terminal after receiving a word addressed to it. For data transmission, baseband transmission systems or carrier modulation transmission systems are used.

The above is an overview of the system shown in FIG. As mentioned above, the central device 11 and each concentrator/distributor 12
The signal transmission time between the line concentrator and distributor 12 differs depending on the position of the line concentrator and distributor 12. Therefore, when each concentrator sends a new word from a terminal to the uplink 14a in response to receiving a word from the central unit 11, a signal collision may occur between the concentrators. . According to the present invention, as will be explained below, in order to avoid such signal collisions and to minimize the blank space between words from the line concentrator and distributor, the start time of sending out words is controlled in the line concentrator and distributor. .

Referring to FIG. 2, the configuration of the central unit 11 according to an embodiment of the present invention is schematically shown, which includes a receiver 21, a word synchronization signal detection circuit 22, a distributor 23, a switch 24, a multiplexing circuit 25 , transmitter 2
6. Subscriber data storage unit 27 and test signal and data transmission start timing control signal generation circuit 28
Equipped with:

The receiver 21 receives signals transmitted from each line concentrator and distributor 12 via the uplink 14a and decodes them into logical data. The output signal of the receiver 21 is
The word synchronization signal SIi (i=1, 2, 3or4) is supplied to the word synchronization signal detection circuit 22 and detects the word synchronization signal SIi (i=1, 2, 3or4) indicating the line concentrator/distributor that generated the received signal.

The received signal is also supplied to a distributor 23. The distributor 23 responds to the word synchronization signal detection circuit 22 and converts the data signals serially sent from the line concentrators and distributors 12 ₁ to 12 ₄ to the line concentrators and distributors 12 ₁ to 12 ₄ .
Distribute the data corresponding to each in parallel form. The distributed data is supplied to the exchange 24, where an exchange process is carried out in a known manner on the basis of the subscriber data from the subscriber data memory 27. Subscriber data includes address information (word synchronization signal) SOi that identifies the line concentrator and distributor, and data that depends on the number of terminals connected to each line concentrator and distributor.
TWi (defines the length of one word assigned to the corresponding line concentrator 12i).

Each exchange 24 is a concentrator/distributor 12 ₁ to 1
₂₄ is output in parallel, and these data are supplied to the multiplexer 25 together with the subscriber data SOi. The multiplexer (MPX) 25 is
The corresponding subscriber data SOi is added as a word synchronization signal to the data addressed to each line concentrator/distributor 12 ₁ at a predetermined timing.
The words addressed to ₁₂₄ are supplied to the transmitter 26 in a time-sharing manner. Transmitter 26 sends the output signal onto downlink 14b after conditioning it into a form suitable for transmission. A clock pulse is superimposed on the output signal to establish synchronization between the central unit and each concentrator.

The control signal generation circuit 28 is provided to avoid collisions between signals sent from the line concentrator and distributor. The control signal generation circuit 28 is
Prior to normal data transmission mode, it operates in test mode and transmission start timing setting mode. In the test mode, the control signal generation circuit 28 generates a test signal addressed to each line concentrator and distributor, and determines the time at which this test signal is sent from the central unit 11 and from each line concentrator and distributor in response to the reception of the test signal. The time difference (delay time) between the sent response signal and the time when it is received by the central device is measured by the line concentrator and distributor. Then, in the transmission start timing setting mode, control data for setting the signal transmission timing of the line concentrator and distributor is calculated based on the delay time measured for each line concentrator and distributor. Then, control data corresponding to each line concentrator/distributor is sent out.

In this embodiment, the test signal sent back from the central unit to each concentrator/distributor in the test mode consists of a word synchronization signal SOi and a common test control signal (DTt). The signal sent back from the distribution device 12i to the central device 11 consists of a word synchronization signal STi. In the transmission start timing setting mode, the signal transmitted from the central device 11 to the line concentrator and distribution device consists of a word synchronization signal SOi and control data DTi. In the test mode and the setting mode, the output signal of the control signal generation circuit 28 is supplied to the transmitter 26 via the OR gate 29.

Here, to explain the subscripts, the central device 11
The signal output from the central unit 1 is set to ``0''.
“I” is assigned to the signal input to 1.

FIG. 3 schematically shows the configuration of the line concentration/distribution device 12. This includes a receiver 31, a word synchronization signal detection circuit 32, a distributor 33, interfaces 34a to 34c, a multiplexer (MPX) 35, a transmitter 36, a control signal detection circuit, and a signal transmission start timing control circuit 38. There is.

The receiver 31 receives the downlink 1 from the central device 11.
4b and decodes it into a level signal. Clock signals φ ₁ and φ ₂ are reproduced simultaneously. A word synchronization signal SOi is detected from the logic level signal by a word synchronization signal detection circuit 32. In response to the detection of the word synchronization signal, the distributor 33 receives the data signal DOi following the synchronization signal, and receives the signals (time-division multiplexed in a predetermined order) for each of the terminals 13a to 13c included in this data signal DOi. ). Distribution of data signals to terminals 13a to 13c takes place via interfaces 34a to 34c. When the terminal 13 is a telephone, the interface 34 is a D-A converter that converts the digital signal from the distributor 33 into an analog signal, and an A-A converter that converts the analog voice signal from the telephone into a digital signal.
- Equipped with a D converter and a hybrid transformer.
However, these are not shown.

Multiplexer 35 is interface 34a
The digital signals from 34c to 34c are time-division multiplexed in a predetermined order. Then, a word synchronization signal SIi is added to the uplink 14 via the transmitter 36.
It is sent to a. In this embodiment, the width of the time slot allocated to signal transmission from each terminal is the same.

As described above, in the present invention, the transmission start timing of each line concentrator and distribution device, in other words, the operation start timing of the multiplexer 35 is controlled. For this purpose, a control signal generation circuit 37 and a transmission start timing control circuit 38 are provided. In the test mode, the control signal generation circuit 37 detects the test control signal following the word synchronization signal in response to the detection of the word synchronization signal by the word synchronization signal detection circuit 32, and immediately outputs the word synchronization signal SIt through the OR gate 39. and supplies it to the transmitter 36. Based on this, the central device 11 measures the delay time of the concentrator and distributor, and after completing the measurement of the delay time of all the concentrators and distributors, calculates control data for each concentrator and distributor 12i. In the transmission start timing setting mode, the control signal detection circuit 37 detects control data in response to detection of a word synchronization signal. The detected control data is supplied to a transmission start timing control circuit 38. The control circuit 38 operates the multiplexer 35 when a time period represented by the control data has elapsed since the word synchronization signal detection circuit 32 detected the word synchronization signal. This prevents data collisions in the central device 11.

The above operation will be explained in more detail.

In Fig. 1, the signal transmission time (delay time) from the central device 11 to the line concentrators 12 ₁ to 12 ₄
are 0.4Δ, 0.9Δ, 1.1Δ and 2.3Δ, respectively.
Δ represents one clock time, which is set appropriately by the system. For example, the time is 8 clock pulses. Time lengths TW ₁ , TW ₂ , TW 3 and _{TW 4} of data signal portions of words assigned to the line concentrators 12 ₁ to 12 ₄ based on subscriber data TWi
is set. Within one frame time, central device 1
Once the order of the words WO ₁ , WO ₂ , and WO ₄ to be sent from the line concentrator 1 to the line concentrators 12 ₁ to 12 ₄ is set, the timing for sending each word is determined.
Test signals for line concentrators and distributors are sent out at the same timing as words for these line concentrators and distributors.

For example, as shown in FIG.
The transmission timings of the test signals for 2 ₂ , 12 ₃ , 12 ₁ and 12 ₄ are set as t ₁ , t ₂ , t ₃ and t ₄ respectively within one frame time. As described above, the test signal consists of the word synchronization signal SOi and the test control signal DTt, and the time length of this control signal is set to be considerably shorter than the time length of the data signal portion in one word. Therefore, after transmitting a test signal, the central device 11 receives a response signal to the transmitted test signal before transmitting the next test signal. The test control signal DTt is configured as "01111111", for example.

As mentioned above, considering the delay time TDi of signal transmission from the central device 11 to each concentrator/distributor,
As shown in FIG. 4B, at time t ₁ the concentrator and distributor 12
As a response signal to the test signal sent to _{SI 2} , the central unit 11 sends a word synchronization signal SI ₂ (0.9Δ
×2+Ts) time delay.

Similarly, the central device 11 includes line concentrators and distributors 12 ₃ ,
Response signals from 12 ₁ and 12 ₄ SI ₃ , SI ₁ , and SI ₄
(1.1Δ×2+Ts), (0.4Δ×2+Ts) and (2.3Δ
×2 + Ts).

In the above, the first term in parentheses is the transmission delay time. Ts is the processing time required in each line concentrator and distributor from receiving the test signal to sending out the response signal.

The central device 11 measures the delay time (2TDi+Ts) for each concentrator and distributor, and detects the maximum delay time (2TDmax+Ts). In this example, the maximum delay time is the concentrator 12 ₄
(4.6Δ+Ts). In this embodiment, the signal transmission start timing of each line concentrator/distributor is controlled so that the delay time of each line concentrator/distributor 12 ₁ to 12 ₄ becomes (2TDmax+Ts). For this purpose, the central device 11 calculates the difference DTi between the position-dependent specific delay time (2TDi+Ts) of each concentrator and distribution device and the maximum delay time (2TDmax+Ts), and corresponds DTi as control data. The data is sent to the line concentrators 12 ₁ to 12 ₄ that are connected to the line concentrators 12 1 to 12 4 . The control data DTi is represented by "0XXXXXXX".

The aforementioned test control signal DTt and control data
The first bit of DTi, "0", is provided to distinguish the following bit from normal data. The 7 bits indicated by X (1ro0) in the control data indicate the delay time added to the inherent delay time of each concentrator/distributor. In this example, the delay times added to the line concentrators 12 ₁ to 12 ₄ are 3.8Δ (=4.6Δ−0.4Δ×2) and 2.8Δ (=4.6Δ−
0.9Δ×2), 2.4Δ(=4.6Δ−1.1Δ×2) and 0(=
4.6Δ−2.3Δ×2). The control data DTi thus calculated is sent out from the transmitter 26 together with the corresponding word synchronization signal SOi at the same timing as the test signal, as shown in FIG.

Based on the control data sent in this way, each line concentrator and distributor controls the signal transmission start timing, and as a result, the time point at which the word is sent from the central unit 11 and the reply word from the line concentrator and distributor that received this word are determined. The time difference between the time of reception by the central unit is made equal for each concentrator.

Next, as described above, by setting the delay time of each line concentrator/distributor, words can be efficiently transmitted from the line concentrator/distributor in the normal data transmission mode. This situation will be explained with reference to the time chart of FIG. The data signal portions DOi and DIi of each word to be transmitted are “1×××
…Indicated by “x”.

As shown in _FIG .
Words WO 2 , WO ₃ to 2 ₃ , _{12 1} and 12 ₄ ,
Assume that WO ₁ and WO ₄ are sent at times t ₁ , t ₂ , t ₃ and t ₄ respectively. As shown in Figure 6B,
The word WO ₂ reaches the receiver 31 of the line concentrator 12 ₂ after a signal transmission time of 0.9Δ. The reply word WI ₂ is then produced by the multiplexing circuit 35 after Ts has elapsed. The signal output from multiplexing circuit 35 is delayed by 2.8Δ. Therefore, _the response word WI ₂ is (0.9Δ+2.8Δ+
Ts) Appears on uplink 14a after a time delay. Similarly, response words WI ₃ , WI ₁ and WI ₄ are respectively (1.1Δ+
2.4Δ+Ts), (0.4Δ+3.8Δ+Ts) and (2.3Δ+
Ts) will appear on the uplink 14a after the lapse of time.
The response word that appeared on uplink 14a
WI ₂ , WI ₃ , WI ₁ and WI ₄ arrive at the receiver 21 of the central unit 11 with a delay of 0.9Δ, 1.1Δ, 0.4Δ and 2.3Δ corresponding to the transmission delay time, respectively.

i.e. words WO ₂ , WO ₃ , WO ₁ and WO ₄
is sent from the central unit 11 until the response words WI ₂ , WI ₃ , WI ₁ and WI ₄ for each are received by the central unit 11 by (0.9Δ×
2+2.8Δ+Ts), (1.1Δ×2+2.4Δ+Ts), (0.4Δ
×2+3.8Δ+Ts) and (2.3Δ×2+Ts) are required. All of these are equal to 4.6Δ+Ts.
Therefore, as shown in Figure 6F, the response word
WI ₂ , WI ₃ , WI ₁ and WI ₄ are words WO ₂ , WO ₃ ,
It is input to the central device 11 with a time delay of (4.6Δ+Ts) from WO ₁ and WO ₄ . That is, it is understood that the words are reliably and efficiently transmitted from the line concentrators 12 ₁ to 12 ₄ to the central unit 11 without signal collisions or spaces between words.

In order to avoid signal collisions due to variations in delay time in the signal transmission path and line concentrator and changes in various characteristics over time, it is possible to provide a space of about 0.1Δ between words sent from the line concentrator and distributor. , enabling more reliable signal transmission. Furthermore, in this embodiment, a space Sp is provided at the end of each frame to facilitate identification between frames. However, since the synchronization signal of the first word of the frame is known, if the frame is identified using this, the above space
SP is not always necessary. In this example,
Although the maximum delay time (2TDmax+Ts) among the delay times of the concentrator/distributor is calculated, the maximum delay time may be determined in advance.

Hereinafter, an embodiment of the test signal and transmission start time control signal generation circuit 28 of the central device 11 will be described with reference to FIG.

The control signal inventing circuit 28 includes the control signal sending means 2
8 ₁ , delay time measuring means 28 ₂ , and test control signal/signal transmission start time control signal generating means 28 ₃ . Clock pulse φ ₂ has a frequency that is, for example, ten times higher than clock pulse φ ₁ .

The control signal sending means 28 ₁ is the shift register 4
1, which includes, in test mode,
The subscriber data (word synchronization signal) SOi from the subscriber data memory 27 and the test control signal DTi from the control signal generating means ₂₈₃ are sent to the line concentrator and distributor 12i.
is read at the time of sending word WOi for. The test signal (SOi+DTt) stored in the shift register 41 is read out serially by the clock pulse _φ1 . That is, during the time length of the test signal, the output of the monostable multivibrator 43 whose output is configured to be "high" and the clock pulse φ ₁ are input to the AND gate 42.
The output of this gate becomes the clock for reading out the shift register 41. A counter 44 and a comparator 45 are provided to measure the duration of the word WOi and to trigger the monostable multivibrator 43. The counter 44 counts the clock pulses φ ₁ , and the counted value is transferred to the comparator 45 from the subscriber data memory 27 (terminal 1 connected to the line concentrator 12i).
(which indicates the time length of word WOi depending on the number of words WOi, etc.). Count value of counter 44
When TWi matches, the comparator 45 triggers the monostable multivibrator 43 to make its output "high" for the time required to send the test signal and clears the counter 44.

The delay time measuring means 28 ₂ uses a clock pulse φ ₂
The circuit includes a counter 46 that counts and is cleared by the output of the comparator 45, and a latch circuit 47 that latches the count value of the counter 46. This latch operation is performed in response to a detection signal (SIi) of the word synchronization signal SIi from the line concentrator/distributor 12i, which is obtained from the word synchronization signal detection circuit 22. Monostable multivibrator 43 is comparator 4
The counter 4 is triggered at the same time as 5.
6 is cleared, the count value of the counter 46 latched by the latch circuit 47 is equal to the test signal SOi.
The time interval from when +DTt is sent until the word synchronization signal SIi is received, that is, the line concentrator 1
2i delay time (2TDi+Ts).

The measured delay time is taken into the microcomputer 48 constituting the control signal generator ₂₈₃ . The microcomputer 48 is the line concentration distribution device 1
The maximum delay time (2TDmax+Ts) after the delay times measured for 2 ₁ to 12 ₄ is detected, and the control data DTi is calculated for each concentrator/distributor 12i as described above. Control data calculated in signal transmission start time setting mode
As in the case of the test control signal DTt, DTi is read into the shift register 41 together with the word synchronization signal SOi, and then sent out.

The shift register 41, monostable multivibrator 43, counters 44, 46, and latch circuit 47 are initialized by the microcomputer 48 at the beginning of the test mode and signal transmission start time setting mode. When the monostable multivibrator 43 is initialized, its output remains "high" for a certain period of time. subscriber data
SOi, TWi, test control signal DTt and control data
DTi is under the control of the microcomputer 48.
The signal is supplied to the control signal sending means 28 ₁ at predetermined timings (t ₁ , t ₂ , t ₃ , t ₄ ).

Referring to FIG. 8, the distributor 33, test and transmission control signal detection circuit 37, and transmission start time control circuit 38 of the line concentrator 12i will be explained.

In each concentrator/distributor 12i, the normal data signal “1×××…××” and the control signal “01111111”
or “0×××××××”.
The distributor 33 is configured to receive only the data signal "XXXX...XX" using the "1" bit following the word synchronization signal. Distributor 33 includes a D-type flip-flop 51 into which received data is input and which is clocked by a word synchronization signal detection signal (SOi). In the normal data transmission mode, when the word synchronization signal SOi is detected, the “1” following the synchronization signal is transferred to the flip-flop 5.
1, which triggers the monostable multivibrator 52. Multi vibrator 52
When triggered, its output goes “high” for the time length of the data signal portion DOi and the AND gate 5
3. Therefore, in the normal data transmission mode, when the word synchronization signal SOi is detected, the following data signal "XXXX...XX" is supplied to the distribution circuit 54 via the AND gate 53. In the case of a control signal, the bit following the word synchronization signal SOi is “0”
, so the monostable multivibrator 52 cannot be triggered. Therefore, no control signal can be provided to the distribution circuit 54.

The control signal detection circuit 37 includes a monostable multivibrator 55 and a shift register 56, which are connected to receive the synchronization signal detection signal (SOi) and received data from the receiver 31, respectively. The monostable multivibrator 55 is triggered by the detection signal (SOi) so that its output remains constant for the duration of the control signal DTt or DTi.
Get “high”. Shift register 56, whose operation is defined by clock _φ1 , reads received data serially and outputs it in parallel. The output of shift register 56 is supplied to comparator 57 and latch circuit 58. The comparator 57 is configured to compare the output of the shift register 56 with the test control signal “01111111” and the control data “0×××××××” and output match signals (DTt) and (DTi). . The match signal (DTt) obtained when the output of shift register 56 matches test control signal DTt triggers monostable multivibrator 60 via AND gate 59 which is enabled by monostable multivibrator 55. As a result, the output of multivibrator 60 is set to "high" for the duration of word synchronization signal SIi, enabling AND gate 61. Clock pulse φ ₁ is supplied to shift register 62 via AND gate 61 . shift register 6
2 receives the word synchronization bit SIi in parallel,
It is sent out in series in response to clock pulse φ ₁ .

Therefore, in the test mode, the line concentrator/distributor 12
When i receives the test signal SOi+DTt, it sends the word synchronization bit in response to the central unit 11.
It is understood that SIi is sent.

In the signal transmission start timing setting mode, the output of the shift register 56 is the control data DTi.
When “0×××××××” is detected, the comparator 57
A coincidence signal (DTi) is outputted from , which is supplied to the latch circuit 58 via the AND gate 63.
As a result, the output of shift register 56 is latched. The control data DTi is detected by the comparator 57 based on the fact that the first bit is "0" and the remaining bits always include at least one "0" bit. be able to.

Control data DTi latched in latch circuit 58
is supplied to the comparator 64 of the signal sending time control circuit 38. A counter 65 is provided which is cleared by the word synchronization detection signal (SOi) and counts clock pulses φ ₂ . The count value of the counter 65 is compared in a comparator 64 with the control data DTi, and if a match occurs, an output signal is produced from the comparator 64, which enables the multiplexer 35 so that the transmission of the signal is started. . In this way, in the normal data transmission mode, in the signal transmission start time setting mode, the signal is latched by the latch circuit 58 and is not transmitted after the time indicated by the control data DTi has elapsed from the time the word synchronization signal SOi is detected. It is understood that this is initiated.

The embodiments of this invention have been described above. Naturally, the present invention is not limited to the above embodiments. For example, it is not necessary to use a pair of transmission lines, and it is natural that a single transmission line may be used for frequency multiplexing, a modification that can be made very easily by those skilled in the art.

Further, the test signal may include only the word synchronization signal component.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a local area network according to one embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a central device according to one embodiment, and FIG. 3 is a diagram showing a line concentration distribution device according to one embodiment. Figure 4 shows the waveforms that appear on the system in the test mode, Figure A shows the test signal sent from the central device to the line concentrator, and Figure B shows the test signal. FIG. 5 is a diagram showing a response signal sent from the line concentrator to the central unit in response to a signal; FIG. 5 is a diagram showing a signal sending time control signal sent from the central unit to the central unit in the signal sending time setting mode;
6 is a waveform diagram for explaining the operation of an embodiment of the present invention, FIG. 7 is a diagram showing the configuration of the control signal generation circuit of FIG. 2, and FIG. 8 is a distribution diagram of the control signal generation circuit of FIG. 3. vessel,
FIG. 3 is a diagram showing the configuration of a control signal detection circuit and a signal transmission control circuit. 11... Central device, 12 ₁ , 12 ₂ , 12 ₃ , 12 ₄
...Concentrator distribution device, 14a, 14b...Transmission line, 13
...Terminal equipment, 28.. Control signal generation circuit, 37.. Control signal detection circuit, 38.. Signal transmission start timing control circuit.

Claims (1)

[Scope of Claims] 1. A plurality of line concentration and distribution terminals are connected to first and second transmission paths connected to a central device, and a plurality of line concentration and distribution terminals are connected to the first transmission line to send signals from the plurality of line concentration and distribution terminals to the central device. A line concentration distribution method for time-divisionally transmitting signals from the central device to the plurality of line concentration and distribution terminals on the second transmission line in a time-division manner, the central The device includes a test signal generating means for sending a test signal to the line concentration distribution terminal, and a delay time until the test signal sent by the test signal generation means returns from the line concentration distribution terminal to the central device again. and a control signal generating means for generating a control signal to the line concentration distribution terminal based on the delay time obtained by the measurement means, the line concentration and distribution terminal generating a control signal for detecting the control signal. and signal transmission time control means for controlling the timing of transmitting the signal to the first transmission line based on the control signal detected by the control signal generation means. . 2. The line concentration and distribution system according to claim 1, wherein the central device has a subscriber data storage unit that stores the connection state of the line concentration and distribution terminals to the first and second transmission paths. 3. A patent characterized in that the signal on the second transmission path has a synchronization signal component corresponding to the line concentration distribution terminal to which this signal is directed, and the test signal generating means generates a test signal having this synchronization signal component. A line concentration distribution system according to claim 1. 4. The line concentration and distribution system according to claim 1, wherein the control signal generating means generates a control signal carrying an amount for delaying the transmission of the signal from the line concentration and distribution terminal. 5. The line concentration and distribution system according to claim 1, wherein the first and second transmission lines are formed by a single transmission line and are used in a frequency multiplexed manner.