JPH11298603A - Subscriber communication system using extension device and the extension device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extension device capable of reporting data line abnormality to an exchange side and an optical subscriber communication system using that extension device. SOLUTION: An exchange 1 and plural network terminals 2 are connected through an exchange side extension device 5 and a subscriber side extension device 6, and the extension devices 5 and 6 are connected by an up data line 8 and a down data line 7 composed of optical fiber cables. An up signal from the network terminal 2 is transmitted through the up data line 8 to the side of the exchange 1, and a down signal from the side of the exchange 1 is transmitted through the down data line 7 to the side of the network terminal 2. When any abnormality such as the disconnection of the down data line 7 occurs, the abnormality on the down data line 7 is detected by a down data line abnormality detecting part 20 of the subscriber side extension device 6, the act bit of the up signal to be transmitted from the side of the network terminal 2 to the side of the exchange 1 is reset from act=1 to 0 by a communication disability reporting part 21, and the up signal is transmitted through the up data line 8 and the exchange side extension device 5 to the side of the exchange 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a subscriber communication system using an extension device for transmitting a digital signal through an ISDN (Integrated Services Digital Network) metal cable and an extension device thereof.

[0002]

2. Description of the Related Art As is well known, for example, an ISDN subscriber communication system capable of providing a subscriber with a multi-channel video signal or audio signal is used. Such a subscriber communication system, as shown in FIG.
An exchange 1 provided in the office and a network terminal (NT) 2 as a subscriber end provided in a plurality of subscriber homes are formed by being connected by a single line by, for example, a metal cable 30 or the like. If the exchange 1 and the network terminal 2 are directly connected by a single line, for example, if the line is a metal cable 30, it is difficult to communicate with the network terminal 2 at a distance of 5 km or more from the exchange 1; There is a problem that the service cannot be provided to the subscribers more than 5 km away from the service.

Therefore, it has been considered that an extension device is provided between the exchange 1 and a plurality of network terminals 2 to improve the service provision to the subscriber. A subscriber communication system as shown is proposed.

In this system, an exchange 1 and a plurality of network terminals 2 are connected to an exchange (LUNT) connected to the exchange 1.
A subscriber (LUL) connected to the extension device 5 and the network terminal 2
T) Connect via the extension device 6, and connect the switch-side extension device 5 and the subscriber-side extension device 6 to an upstream data line (an upstream data high-speed line) using, for example, an optical fiber cable as an optical line.
8 and a downlink data line (downlink data high-speed line) 7. The uplink signal from the network terminal 2 is transmitted to the subscriber-side extension device 6, the uplink data line 8, and the switch-side extension device 5.
Are sequentially transmitted to the exchange 1 side, and the downstream signal from the exchange 1 side is transmitted to the network terminal 2 side sequentially through the exchange side extension device 5, the downstream data line 7, and the subscriber side extension device 6. .

[0005] In any of the subscriber communication systems shown in FIGS. 3 and 4, a terminal (TE) 9 is connected to the network terminal 2 via an S / T point 10. FIG.
In the figure, 3 indicates a local U point, 4 indicates a remote U point, the exchange 1 is connected to the exchange side extension device 5 via a local U point 3 by a metal cable, and each network terminal 2 is It is connected to the subscriber-side extension device 6 via a U-point 4 by a metal cable.

As shown in the subscriber communication system shown in FIG. 3, when an exchange-side extension device 5 and a subscriber-side extension device 6 are provided and these extension devices 5 and 6 are connected by data lines 7 and 8, for example, A plurality of pieces of information from the network terminator 2 can be multiplexed by the subscriber-side extension device 6, transmitted to the exchange-side extension device 5 through the upstream data line 8, and transmitted to the exchange 1 via the local U point 3. Then, a plurality of information from the exchange 1 is multiplexed by the exchange-side extension device 5 and transmitted to the subscriber-side extension device 6 through the downstream data line 7 to the network terminal 2 via the remote U point 4. To be able to send
For example, it is possible to provide a service to a network terminal 2 which is 20 km or more away from the exchange 1.

[0007]

However, in the subscriber communication system as shown in FIG. 3, the upstream signal is transmitted through the upstream data line 8 to the subscriber extension device 6.
Side to the exchange-side extension device 5 side, and the downlink signal is transmitted from the exchange-side extension device 5 side to the subscriber-side extension device 6 side through the downlink data line 7. When only the downlink data line 7 among the downlink data lines 7 is disconnected, the downlink signal cannot be transmitted from the exchange 1 to the network termination 2 side, but the uplink signal from the network termination 2 side passes through the uplink data line 8. It is transmitted to the exchange 1. Therefore, the exchange 1 cannot know the abnormality such as the disconnection of the downlink data line 7.

Therefore, when such an abnormality occurs, there arises a problem that the abnormality cannot be promptly dealt with, although the station having the exchange 1 must deal with the abnormality.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to connect an exchange-side extension device and a subscriber-side extension device in a subscriber communication system using the extension device. It is an object of the present invention to provide a subscriber communication system using an extension device and an extension device thereof, which enable the exchange to know that communication is not possible when an abnormality such as disconnection of a downlink data line occurs in the communication system.

[0010]

In order to achieve the above-mentioned object, the present invention has the following structure to solve the problem. In other words, a subscriber communication system using the extension device of the present invention comprises an exchange-side extension device in which a switch and a plurality of subscriber ends are connected to the exchange side and a subscriber-side extension device connected to the subscriber end. Connected via an extension device, wherein the exchange-side extension device and the subscriber-side extension device are connected by an upstream data line and a downstream data line,
The uplink signal from the subscriber end side is transmitted to the exchange side through the subscriber extension device, the uplink data line, and the exchange side extension device in order, and the downlink signal from the exchange side is exchanged with the exchange side extension device. What is claimed is: 1. A subscriber communication system using an extension device for transmitting a downlink data line and a subscriber extension device in order to a subscriber end side, wherein at least one of the exchange side extension device and the subscriber extension device A downlink failure detection unit that detects the failure of the downlink data line, and a communication failure notification unit that informs the exchange side that communication is not possible when the failure of the downlink data line is detected by the downlink failure detection unit. It is a means to solve the problem with the provided configuration.

The first invention of an extension device is an extension device used in a subscriber communication system using the extension device having the above-mentioned configuration, wherein the extension device is connected to a subscriber end. The apparatus is provided with an upstream signal transmission / reception section for receiving the upstream signal from the subscriber end side, transmitting the upstream signal through an upstream data line, and transmitting the upstream signal to a switching side extension device connected to the switching side, and a switching side extension. The apparatus receives an upstream signal added from the subscriber extension apparatus side and transmits the upstream signal to the exchange, and receives a downstream signal from the exchange side and passes the downstream signal through the downstream data line to join. A downstream signal transmitting / receiving section for transmitting to the subscriber side extension apparatus; a downstream signal transmitting / receiving section for receiving the downstream signal applied from the switching side extension apparatus side and transmitting the downstream signal to the subscriber end side. Is provided At least one of the switch-side extension device and the subscriber-side extension device communicates with a downlink abnormality detector that detects an abnormality of the downlink data line, and communicates when the downlink data abnormality is detected by the downlink abnormality detector. This is a means for solving the problem by having a configuration having a communication failure notification unit for notifying the exchange that the connection is impossible.

Further, according to the second invention of the extension device, in addition to the configuration of the first invention, the communication failure notification unit joins when a downlink data line abnormality is detected by the downlink line abnormality detection unit. This is a means for solving the problem by having a configuration in which a communication abnormality detection signal is added to a signal transmitted from the user end to the exchange side and transmitted to the exchange side to notify the exchange side that communication is not possible.

Further, in the third aspect of the present invention, in addition to the configuration of the first or second aspect, the communication failure notification unit may be configured to transmit an uplink signal transmitted from the subscriber end to the exchange. This is a means for solving the problem by having a configuration as a signal reset unit for resetting at least one of the act bit and the sai bit to 0.

Further, in the fourth invention of the extension device, in addition to the configuration of the first, second or third invention, the exchange-side extension device may detect an abnormality in an uplink data line. And an uplink abnormality signal transmitting section for outputting an uplink abnormality signal for notifying the exchange of the abnormality of the uplink data line when the abnormality of the uplink data line is detected by the uplink abnormality detection section. It is a means to solve the problem with.

In the present invention having the above-described structure, at least one of the switch-side extension device and the subscriber-side extension device has a down-link abnormality detecting section for detecting an abnormality of the down-link data line, and the down-link abnormality detection section detects the down-link data line. And a downlink data line that connects the switch-side extension device and the subscriber-side extension device to each other since the switch has a communication failure notification unit that informs the exchange that communication is not possible when an abnormality is detected. When the downstream data line is disconnected, even if data is transmitted from the subscriber end to the exchange through the upstream data line, at least one of the exchange side extension device and the subscriber side extension device side The communication failure notification unit provided on the communication side informs the exchange that communication is impossible. Therefore, it is possible for the exchange to know that communication is not possible. For example, it is possible to promptly deal with the abnormality at the station where the exchange is provided, and the above-mentioned problem is solved.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a subscriber communication system using an extension device according to the present invention. In FIG. 1, the same names as those of the conventional example and the subscriber communication system shown in FIG. The parts are denoted by the same reference numerals.

The subscriber communication system of this embodiment is
As in the subscriber communication system shown in FIG.
And a plurality of network terminations 2 are connected via an exchange-side extension device 5 and a subscriber-side extension device 6, and the exchange-side extension device 5 and the subscriber-side extension device 6 are connected to an upstream data line 8 using, for example, an optical fiber cable. It is connected to the downlink data line 7 and has almost the same configuration as that of the subscriber communication system shown in FIG.

As shown in FIG. 1, the switch-side extension device 5 and the subscriber-side extension device 6 each include a plurality of U-point interface chips 11, a time-division switch 12, and a CPU (Central) functioning as a control device. Proce
ssing Unit) 13 and a high-speed line framer chip 14.

Further, in this embodiment, the subscriber-side extension device 6 receives the upstream signal from the network terminal 2 and passes this upstream signal to the upstream data line 8 to extend the switching device. An upstream signal transmitting / receiving section for transmitting to the apparatus 5 and a downstream signal transmitting / receiving section for receiving a downstream signal applied from the switching side extension apparatus 5 and transmitting the downstream signal to the network terminal 2 are formed. Is an upstream signal transmitting / receiving section that receives an upstream signal applied from the subscriber side extension device 6 and transmits the upstream signal to the exchange 1 side, receives a downstream signal from the exchange 1 side, and passes this downstream signal through the downstream data line 7. A downstream signal transmitting / receiving unit for transmitting to the subscriber-side extension device 6 is formed.

The U-point interface chip 11 of the exchange-side extension device 5 transmits and receives data at the local U-point 3, and the U-point interface chip 11 of the subscriber extension device 6 has a U-point interface chip of the remote U point 4. It transmits and receives data. Each U point data includes user data (2
B + D), data called overhead bits for monitoring and controlling the status of the apparatus are included. The U-point interface chip 11 passes the user data out of the received U-point data through the path. A, the data is transmitted to the time division switch 12, and the overhead bit data is transmitted to the CPU 13 through the path B.

After reading the overhead bit data transmitted from the U-point interface chip 11, the CPU 13 transmits this data to the time division switch 12 through the path C.

The time division switch 12 receives data transmitted through the respective paths A and C, multiplexes the data, and transmits the multiplexed data to the high-speed framer chip 14. If necessary, maintenance data for maintenance data between the exchange-side extension device 5 and the subscriber-side extension device 6 are also multiplexed by the time division switch 12.

The high-speed framer chip 14 converts the multiplexed data received from the time-division switch 12 into frames. The high-speed framer chip 14 of the exchange-side extension device 5 passes the framed data through the downstream data line 7. To the high-speed framer chip 14 of the subscriber-side extension device 6, and the high-speed framer chip 1 of the subscriber-side extension device 6
4 transmits the framed data to the high-speed framer chip 14 of the exchange-side extension device 5 through the upstream data line 8.

The high-speed framer chip 14 also has a function of deframing the data received from each of the data lines 7 and 8, and the high-speed framer chip 14 of the exchange-side extension device 5 The received data is deframed and transmitted to the time division switch 12, and the high-speed framer chip 14 of the subscriber-side extension device 6 deframes the data received from the downstream data line 7 and transmits it to the time division switch 12.

The time division switch 12 demultiplexes the data received from the high-speed framer chip 14 and passes the user data through the path A to the U-point interface chip 1
1 and transmits the overhead bit data to the CPU 13 through the path C.

After reading the overhead bit data received from the time division switch 12, the CPU 13 transmits this data to the U point interface chip 11 through the path B.

The U-point interface chip 11 of the exchange-side extension device 5 transmits the received U-point data (user data and overhead bit data) to the exchange 1 through the local U-point 3 and transmits the data to the subscriber-side extension device 6. The U point interface chip 11 transmits the received U point data to each network terminal 2 through the remote U point 4.

In this embodiment, the high-speed framer chip 14 of the subscriber-side extension device 6 is provided with a down-link abnormality detection section 20 for detecting an abnormality such as disconnection of the down-link data line 7. When detecting the abnormality of the downlink data line 7, the detection unit 20 adds a downlink data line abnormality detection signal to the communication failure notification unit 21 of the CPU 13.

When the downlink failure detecting section 20 detects an abnormality of the downlink data line 7, the communication failure notification section 21 receives the downlink data line abnormality detection signal added from the downlink abnormality detecting section 20 and performs network termination. Switch 1 from 2 side
By transmitting a communication abnormality detection signal to the signal transmitted to the exchange and transmitting the signal to the exchange 1, it is notified to the exchange that communication is impossible. More specifically, the communication failure notification unit 21 activates the act of the uplink signal transmitted from the network terminal 2 to the exchange 1.
The signal reset section resets a bit to 0 (act bit mask).

When the downlink data line 7 returns to normal, the downlink data line abnormality detection signal applied to the communication failure notification unit 21 by the downlink failure detection unit 20 is released, and the communication failure notification unit 21 activates The bit mask is released.

The act bit is a part of the overhead bit data and conforms to ANSI standard (T1.601).
1992), in a state in which frame exchange between the exchange 1 and the network terminal 2 can be established (a state in which data transmission is possible), and in the remote U point 4 and the S / T point 10
In the state where transparent communication is possible, ac
In the state where the signal value of t = 1 is transmitted toward the exchange 1 side, while at least one of the S / T point 10 and the remote U point 4 has some kind of failure and the transparent communication is impossible. , The signal value of act = 0 is transmitted from the network terminal 2 to the exchange 1 side.

Normally, act =
1 is roofed back by the exchange 1, and communication is enabled when the network terminal 2 receives the act backed act = 1, while when the act = 0 is transmitted from the network terminal 2, the exchange 1 In response to act = 0, S /
It is configured to recognize that a failure has occurred in at least one of the T point 10 and the remote U point 4.

Therefore, in this embodiment, as described above,
When an abnormality of the downlink data line 7 is detected by the downlink abnormality detection unit 20 provided in the high-speed framer chip 14 of the subscriber extension device 6, the communication failure notification unit 21 is transmitted from the network terminal 2 to the exchange 1. By resetting the act bit of the upstream signal to 0, act = 0 is transmitted to the exchange 1, and the act 1 is received by the exchange 1, thereby notifying the exchange 1 that communication is impossible.

In the embodiment, for example, the local U point 3 and the remote U point 4 are each provided with an appropriate number of lines up to eight lines.

The present embodiment is configured as described above. The functions of the U-point interface chip 11, time-division switch 12, CPU 13, and high-speed framer chip 14 are also used in the present embodiment to add the subscriber shown in FIG. Similarly to the mobile communication system, the upstream signal from the network terminal 2 is transmitted through the subscriber-side extension device 6, the upstream data line 8, and the exchange-side extension device 5 to the exchange 1 side, and is transmitted from the exchange 1 side. The signal is transmitted to the network terminator 2 through the exchange-side extension device 5, the downstream data line 7, and the subscriber-side extension device 6 in this order. In this embodiment, an abnormality such as disconnection of the downstream data line 7 occurs. In some cases, the downlink data line abnormality detector 20 of the subscriber-side extension device 6 detects an abnormality of the downlink data line 7.

When the abnormality of the downlink data line 7 is detected by the downlink data line abnormality detector 20,
As shown in FIG. 2, the communication failure notification unit 21
Ac of an upstream signal transmitted from the network terminal 2 to the exchange 1
The t bit is reset from act = 1 to 0, and act =
A signal value of 0 is transmitted from the subscriber-side extension device 6 to the exchange 1 through the upstream data line 8 and the exchange-side extension device 5. Then, when the downlink data line 7 is restored after the abnormality of the downlink data line 7 is dealt with, the communication failure notification unit 21
Is canceled.

According to this embodiment, by the above operation,
When an abnormality occurs in the downlink data line 7, the exchange 1 is configured to detect the abnormality and inform the exchange 1 of the abnormality. And the station on which the exchange 1 is provided can quickly cope with the abnormality. When the downlink data line 7 returns to normal due to the countermeasure for the abnormality, the act
Since the bit mask is released, for example, exchanges 1 and 2
Communication with the network terminal 2 distant by 0 km or more is performed by the exchange-side extension device 5, the subscriber-side extension device 6, the downlink data line 7,
It can be restarted via the upstream data line 8.

It should be noted that the present invention is not limited to the above-described embodiment, but can adopt various embodiments. For example, in the above-described embodiment, both the downlink abnormality detection unit 20 and the communication failure notification unit 21 are provided on the subscriber-side extension device 6 side. For example, as shown by the broken line in FIG. One or both of the communication unit 20 and the communication failure notification unit 21 may be provided on the exchange-side extension device 5 side, or the downlink abnormality detection unit 20 and the communication failure notification unit 21 may be provided on the subscriber-side extension device 6 and the exchange-side extension device 5 may be provided.

As shown by the broken line in FIG. 1, the exchange-side extension device 5 has an uplink abnormality detecting section 22 for detecting an abnormality of the uplink data line 8, and the uplink abnormality detecting section 22 detects the uplink data line 8. When an abnormality is detected, an uplink abnormality signal transmitting unit 23 that outputs an uplink abnormality signal for notifying the exchange 1 of the abnormality of the uplink data line 8 may be provided. When this uplink abnormal signal is transmitted to the exchange 1 as a signal that can be distinguished from a signal for notifying the abnormality of the downlink data line 7, the exchange 1 can detect the abnormality of the downlink data line 7 and the abnormality of the uplink data line 8. Since it is possible to reliably recognize and recognize the abnormalities, it is easier to deal with the abnormalities of the data lines 7 and 8, and it is possible to more quickly and reliably deal with the abnormalities.

Further, in the above embodiment, the communication failure notification unit 21 is a signal reset unit that resets the act bit from 1 to 0, and changes the act bit from 1 to 0 when an abnormality of the downlink data line 7 is detected. To the exchange 1 side, but the communication failure notification unit 21
In place of the bits, among the overhead bit data transmitted from the network terminal 2 to the exchange 1, the sai bit indicating the state of the S / T point 10 (sai = 1 when communication is possible at the S / T point 10, communication Is impossible when
ai = 0) may be set as a signal reset unit for resetting to 0, or both the act bit and the sai bit may be reset to 0.

Further, in the above embodiment, the communication failure notifying section 21 resets the act bit transmitted from the network terminal 2 to the exchange 1 when the abnormality of the downlink data line 7 is detected. The exchange 1 is informed that communication is not possible.
When an abnormality of the downlink data line 7 is detected, for example,
A unique signal indicating that the downlink data line 7 is abnormal may be transmitted to the exchange 1 to inform the exchange 1 that communication is impossible.

Further, the present invention including the above-described embodiment is added to the remote knockdown type subscriber communication system provided with the abnormality notification means of the downlink data line 7 previously proposed by the present applicant. It can also be applied. In this remote knockdown type subscriber communication system, a failure detection unit for the downlink data line 7 is provided on the subscriber side extension device 6 side. Is used to transmit the abnormality detection information to the CPU 13 of the exchange-side extension device 5 side. At this time, the local U point 3 is forcibly disconnected to notify the exchange 1 of the abnormality of the downlink data line 7 by making communication impossible. It is.

In this system, the local U point 3
After a certain period of time elapses after the disconnection, the local U point 3 returns to the normal state. For example, the act bit and the sai bit transmitted from the network terminal 2 to the exchange 1 are set to 0 as in the above embodiment. If the remote U point 4 and the S / T point 10 are normal without being reset (bit mask) and transmitted to the exchange 1 side, even if the downlink data line 7 has not been restored yet, act = 1, The signal value of sai = 1 is transmitted to the exchange 1 side.

Therefore, if the downlink data line 7 has not been restored even after the predetermined time has elapsed, the exchange 1 cannot recognize the abnormality of the downlink data line 7 and erroneously recognizes that communication is possible. However, if the present invention is applied to this remote knockdown type subscriber communication system, even after the local U point 3 recovers, the act bit and the sai bit remain until the downlink data line 7 recovers. Since one or both of the bits are reset to 0 and transmitted to the exchange 1, the erroneous recognition as described above can be prevented.

Further, the subscriber communication system using the extension device of the present invention is a system in which the exchange 1 and a plurality of network terminals 2 are connected via the exchange-side extension device 5 and the subscriber-side extension device 6. The number of the local U points 3 and the number of the remote U points 4 and the number of the network terminations 2 are not particularly limited and may be set as appropriate.

Further, the subscriber communication system of the present invention is not limited to the one in which the downstream data line 7 and the upstream data line 8 are formed by optical lines as in the above-described embodiment. A communication system in which the downlink data line 7 and the uplink data line 8 are formed by lines may be used.

[0047]

According to the present invention, at least one of the exchange-side extension device and the subscriber-side extension device interposed between the exchange and the subscriber's end unit has a downlink abnormality detecting the abnormality of the downlink data line. Since the detection unit and the downlink failure detection unit have a communication failure notification unit that informs the exchange that communication is not possible when an abnormality in the downlink data line is detected by the downlink failure detection unit, When the downlink data line of the uplink data line and the downlink data line connecting the subscriber-side extension device is disconnected, even if data is transmitted from the subscriber end to the exchange through the uplink data line. In addition, it is possible to reliably notify the exchange side that communication is impossible from the communication failure notification unit provided on at least one of the exchange side extension device and the subscriber side extension device side.

Therefore, according to the present invention, since it is possible to know that the communication is not possible on the exchange side, it is possible to promptly cope with abnormalities, for example, by the station provided with the exchange.

Further, the communication failure notification unit, when a downlink data line abnormality is detected by the downlink line abnormality detection unit, adds a communication abnormality detection signal to a signal transmitted from the subscriber end to the exchange. According to the extension device of the present invention, which is configured to notify the exchange that transmission is impossible by transmitting the signal to the exchange, communication to the exchange is performed using a signal transmitted from the subscriber end to the exchange. Since it is possible to notify that the communication is not possible, it is possible to perform the notification that the communication is not possible very efficiently, thereby simplifying the system configuration of the subscriber communication system using the extension device. it can.

Further, in the extension device according to the present invention, the communication failure notification unit is a signal reset unit for resetting at least one of the act bit and the sai bit of the upstream signal transmitted from the subscriber end to the exchange. According to this, a very simple configuration, such as resetting the act bit and the sai bit signal, can reliably inform the exchange that communication is impossible. Therefore, the configuration of the extension device and the configuration of the subscriber communication system using the extension device can be greatly simplified, and the cost of the extension device and the communication system can be reduced.

Further, the exchange-side extension device includes an uplink abnormality detecting section for detecting an abnormality of the uplink data line, and an exchange abnormality when the abnormality of the uplink data line is detected by the uplink abnormality detecting section. According to the extension apparatus of the present invention having an uplink abnormal signal transmitting section for outputting an uplink abnormal signal for informing the side, not only the abnormalities of the downlink data lines but also the abnormalities of the uplink data lines can be reliably confirmed at the exchange side. Can be more reliably prompted to deal with the abnormalities of the subscriber communication system, and by distinguishing the abnormalities of the downstream data line and the abnormalities of the upstream data line and reporting to the exchange, It is possible to more quickly cope with the abnormality of the data line.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram showing an embodiment of a subscriber communication system using an extension device according to the present invention.

FIG. 2 is an explanatory view showing an abnormality notification operation when an abnormality occurs in the downlink data line 7 in the embodiment.

FIG. 3 is an explanatory diagram showing an example of a subscriber communication system using an extension device devised by the present applicant.

FIG. 4 is an explanatory diagram showing an example of a conventional subscriber communication system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Switch 2 Network termination 3 Local U point 4 Remote U point 5 Switch side extension device 6 Subscriber extension device 7 Downlink data line 8 Uplink data line 10 S / T point 20 Downlink error detection unit 21 Communication failure notification unit 22 Uplink Line abnormality detection unit 23 Uplink abnormality signal transmission unit

Claims (5)

[Claims] An exchange and a plurality of subscriber terminals are connected via an exchange-side extension device connected to the exchange and a subscriber-side extension device connected to the subscriber end. An apparatus and a subscriber-side extension device are connected by an uplink data line and a downlink data line, and an uplink signal from the subscriber end is transmitted to the subscriber-side extension device, the uplink data line, and the exchange side. An extension device is used to transmit the signal to the exchange side through the device in order, and to transmit the downstream signal from the exchange side to the subscriber end side through the exchange side extension device, the downlink data line and the subscriber extension device in order. A subscriber communication system, wherein at least one of the switch-side extension device and the subscriber-side extension device has a downlink abnormality detector that detects an abnormality of the downlink data line, and the downlink data has been detected by the downlink abnormality detector. Times A subscriber communication system using an extension device, comprising: a communication failure notification unit that informs the exchange that communication is impossible when a line abnormality is detected. 2. An extension device for use in a subscriber communication system using the extension device according to claim 1, wherein the subscriber-side extension device connected to the subscriber-end side includes the subscriber-end portion. An upstream signal transmitting / receiving unit is provided for receiving an upstream signal from the mobile station and transmitting the upstream signal through an upstream data line to an exchange-side extension device connected to the exchange side. The exchange-side extension device includes a subscriber extension device. An upstream signal transmitting / receiving section for receiving an upstream signal applied from the mobile station and transmitting the downstream signal to the exchange side; and receiving a downstream signal from the exchange side and transmitting the downstream signal to the subscriber extension device side through the downstream data line. A downstream signal transmission / reception unit is provided, and the subscriber-side extension device is provided with a downstream signal transmission / reception unit that receives a downstream signal applied from the exchange-side extension device side and transmits the downstream signal to the subscriber end side. Extension equipment and subscription At least one of the user-side extension devices is configured to detect a failure of the downlink data line, and to the exchange side that communication is not possible when the abnormality of the downlink data line is detected by the downlink abnormality detection unit. An extension device having a communication failure notification section for notifying. 3. A communication failure notification unit which, when an abnormality of a downlink data line is detected by a downlink abnormality detection unit, carries a communication abnormality detection signal on a signal transmitted from the subscriber end to the exchange to exchange. 3. The extension device according to claim 2, wherein the transmission to the exchange notifies the exchange that communication is impossible. 4. The communication failure notification section is a signal reset section for resetting at least one of an act bit and a sai bit of an uplink signal transmitted from the subscriber end to the exchange side to 0. The extension device according to claim 2 or 3. 5. An exchange-side extension device comprising: an uplink abnormality detecting section for detecting an abnormality of an uplink data line; and an abnormality of the uplink data line when the abnormality of the uplink data line is detected by the uplink abnormality detecting section. 5. The extension device according to claim 2, further comprising an uplink abnormal signal transmitting section for outputting an uplink abnormal signal for notifying the extension device.