JPH0286391A - Isdn local communication system - Google Patents

Abstract

PURPOSE:To attain mutual communication without an ISDN network between plural terminal equipments when a terminal equipment is not in the communication state with a network terminal equipment by providing a relay loopback device having a relay function, a loopback function and a switching function switching both the functions. CONSTITUTION:A relay loopback device 3 installed between a terminal equipment 1 and a network terminator 2 relays a signal from the terminal equipment 1 to the network terminator 2 and a signal from the network terminator 2 to the terminal equipment 1 in the case of communication from the terminal equipment 1 to the network terminator 2. When the terminal equipment 1 does not communicate the network terminator 2, the relay loopback deice 3 includes the signal from the terminal equipment 1 into a signal sent to the terminal equipment 1. Thus, the information is looped back and a specific pattern representing the information loopback state is added and the resulting signal is sent. Thus, when the terminal equipment 1 and the network terminator 2 are not communicated with each other, the terminal equipments 1 are communicated mutually not via the ISDN network.

Description

[Detailed Description of the Invention] [Summary] Regarding the ISDN local communication method for mutual communication between a plurality of terminal devices connected to ISDN in a bus wiring format, The purpose of this system is to enable terminal devices to communicate with each other without going through an ISDN network, and to transmit signals between the terminal devices and the network terminating device between a plurality of terminal devices and the network terminating device. A relay function that relays a signal, a loopback function that adds a special pattern indicating that it is in a loopback state to the signal received from the terminal device, and sends it to the terminal device, and the terminal device and the network termination device listed below are in a communication state. The relay function has a switching function that detects whether or not the
A return device is provided, and when the terminal device is out of communication with the network terminal device, IS is transmitted between the plurality of terminal devices.
It is configured to perform mutual communication without going through DNI.

[Industrial Application Field] The present invention is applied to ISDN (Integrated
5services Digital Network
: Service integrated digital network) IS that performs mutual communication between multiple terminal devices connected to W4 in a bus wiring format.
Regarding DN local communication system.

[Conventional technology]

The ISDN basic interface consists of two information channels (hereinafter referred to as B channels) having a transmission rate of 64 bps and a signal channel (hereinafter referred to as D channel) mainly transmitting call control information and the like and having a transmission rate of 16 Kbps. It is a digital interface having one channel, and is designed so that a plurality of terminal devices connected in a bus wiring format can communicate with the ISDNM4 at the same time.

FIG. 6 is a block diagram showing the bus wiring format of the ISDN basic interface. A plurality of terminal devices 1 are connected to a network termination device 2 via a bus B, and information is transmitted in different frame structures depending on the transmission direction. ing. Terminal device 1
is a device having an interface compliant with the ISDN basic interface specifications, and the network termination device 2 corresponds to a digital line termination device (DSU) and a private branch exchange (PBX) in a public network.

FIG. 7 is a diagram showing the frame structure of the basic interface. FIG.
) shows the structure of a frame FB transmitted from the terminal device 1 to the network terminating device 2. Both frames FA and FB consist of 48 bits (250 μs) per frame, and have a transmission speed of 192 kbps, 81 bits and 82 bits for the B channel, the D bit for the D channel, the F bit for frame synchronization, and It consists of L bits for DC balance, etc. The E bit of the frame FA is the D bit of the frame FB received from the terminal device 1 which is returned as is by the network terminal device 2 in order to perform D channel contention control.

[Problem to be solved by the invention]

By the way, since only the communication means between the terminal device 1 and the ISDN 14 are defined by the specifications and procedures of the ISDN basic interface, the terminal devices 1 are
When communicating without going through a DN network, it is necessary to prepare an interface different from the basic interface. However, providing the terminal device 1 with another interface not only increases the cost of the terminal device 1, but also requires connecting the terminal devices 1 with a cable different from the basic interface cable. Further, there is a problem that communication processing in the terminal device 1 becomes complicated.

An object of the present invention is to enable terminal devices to communicate with each other on an interface that conforms to the specifications of the ISDN basic interface without going through ISDN.

[Means to solve the problem]

As shown in the principle diagram of FIG. 1, a plurality of terminal devices 1 are connected to a network termination device 2 in a bus wiring format, and the terminal device 1 and the network Relay function for relaying signals between the terminal devices 2, the terminal device 1 mentioned above
A loopback function adds a special pattern indicating a loopback state to a signal received from the terminal and sends it to the terminal device 1, and detects whether or not the terminal device 1 and the network terminating device 2 are in a communication state. A relay/return device 3 having a switching function for switching between the relay function and the return function is provided, and when the terminal device 1 is in a non-communication state with the network terminal device 2, the plurality of terminal devices 1
The configuration is such that mutual communication can be performed between the two without going through the ISDN network.

[Function] When the terminal device 1 communicates with the network termination device 2, the relay/return device 3 installed between the terminal device 1 and the network termination device 2 transmits the signal from the terminal device 1 to the network termination device. 2, the signals from the network termination device 2 are relayed to the terminal device 1 (FIG. 1A).

When the terminal device 1 does not communicate with the network terminating device 2, the relay/turnback device 3 loops back the information by including the signal from the terminal device 1 in the signal transmitted to the terminal device 1, and also loops back the information. A special pattern indicating the status is added and transmitted (FIG. 1B).

In this way, by installing the relay/return device 3, when the terminal device 1 and the W4 termination device 2 are in a non-communication state, the terminal devices 1 can communicate with each other using ISDN! It becomes possible to communicate with each other without going through i1.

〔Example〕

FIG. 2 is a block diagram showing an embodiment of the ISDN local communication system according to the present invention, in which a plurality of terminal bags W1 having an ISDN basic interface are connected to a network termination device 2 via a bus B, and a terminal device A relay/return device 3 is installed between the network terminal device 1 and the network termination device 2.

Each of the plurality of terminal devices 1 includes a receiving section 10 that receives signals transmitted on bus B, a B channel receiving section 11 that receives the B1 bit and 82 bits from the received signal, and a receiving section 11 that receives the B1 bit and 82 bits from the received signal. A D channel control unit 13 receives D bits and E bits from a switch 12, detects whether or not the received D bits include a special pattern, and switches the switch 12 based on the detection result. It has a special pattern detection section 14, and further includes a transmitting section 16 and a receiving section 1 that transmits 81 bits and 82 bits outputted from the B channel transmitting section 15 and the D bit outputted from the D channel control section 13 onto the bus B.
It has a comparison section 17 that compares the E bit received at 0 with the D bit output from the D channel control section 13 and outputs the comparison result to the D channel control section 13.

The relay/return device 3 includes a receiving unit 30 that receives signals transmitted from the network terminating device 2, a transmitting unit 31 that sends signals to the network terminating device 2, and a receiving unit that receives signals transmitted on the bus B. section 32, a transmission section 33 that sends a signal onto the bus B, a control section 34 that switches the relay/return device 3 to relay mode or return mode, and further includes three switches 35 whose switching is controlled by the control section 34, 3
6 and 37, Bl from among the signals received by the receiving section 32
, B2. It has a channel extraction section 38 that extracts the D bit, a special pattern generation section 39 that generates a special pattern indicating the loopback mode, and a frame generation section 40 that configures the frame sent to the bus B in the loopback mode. It also has a clock extraction section 41 that extracts a clock from a signal sent from the network termination device 2 and a clock generation section 42 that generates an internal clock. The clock output of the section 41 is output to the clock generating section 42 in the loopback mode.
The clock outputs are supplied to the transmitting sections 31 and 33, respectively, and are used as clocks for the signals to be sent.

Next, the operation of this embodiment will be explained with reference to the flowcharts shown in FIGS. 3 and 4.

First, when the terminal device l and the network termination device 2 are in a communication state, the relay/return device 3 is set to relay mode,
Switches 35, 36 and 37 are connected to the fixed terminal a side. In this state, the signal from the network termination device 2 received by the receiver 30 is transmitted to the bus B via the switch 36 and the transmitter 33, and the signal from the bus B received by the receiver 32 is transmitted to the switch 37 and It is transmitted to the network terminal device 2 via the transmitter 31. When transmitting signals from the transmitting sections 31 and 33, the clocks extracted by the clock extracting section 41 are used to transmit the signals.

In the terminal device 1, the receiving unit 10 receives the signal transmitted on the bus B, and performs D channel control to determine whether the transmitted signal is a signal addressed to itself based on the call information included in the D bit. It is identified in section 13.

If the signal is addressed to the terminal itself, the B1 and 82 bits received by the receiver 10 are received by the B channel receiver 11, and if the signal is not addressed to the terminal, it is not received as it is addressed to another terminal device.

When transmitting a signal from the terminal device 1 onto the bus B, the E bit received by the receiving section 10 and the D bit output from the D channel control section 13 are compared in the comparing section 17, and if they match, the own terminal Since the device is accessing the D channel, this D bit and the B1 and B2 bits from the B channel transmitter 15 are sent onto the bus B from the transmitter 16. If they do not match, the other terminal device
Since the channel is being accessed, it will not be transmitted.

As mentioned above, the E bit is a pit that returns the D bit received from the terminal device 1 as is and sends it to the terminal device 1 in order to perform D channel contention control, so the E bit is a pit that is sent out from the own terminal device 1. This is because if the received E bit and the received E bit fail, it means that the own terminal device 1 is accessing the D channel.

In this way, in the relay mode, the relay/return device 3 simply relays signals, so the terminal device 1
can communicate with the network termination device 2 using the same procedure as when the relay/return device 3 is not installed.

After the communication between the terminal device 1 and the network termination device 2 is completed, the control unit 34 of the relay/return device 3 detects a stop signal sent from the terminal device 1 and the network termination device 2, respectively (step 30 in FIG. 3). ), or detects that the outputs of the terminal device 1 and the network termination device 2 are in a no-signal state, the control unit 34 switches the switches 35, 36 and 37 to the fixed terminal side (step 31), and starts frame generation. The special pattern generating section 40 is activated (step 32) to standby for a certain period of time (step 33), and then the special pattern generating section 39 is activated (step 34) and set to return mode.

When the relay/return device 3 switches to the return mode, the signal from the terminal device 1 received by the receiver 32 is sent to the transmitter 33 via the channel extractor 38, frame generator 40, and switch 36, and then sent to the transmitter 33. At 33, the sent signal is sent back to the terminal device 1 together with the clock output of the clock generator 42.

The details of this folding process will be explained with reference to the frame diagram shown in FIG. First, the channel extractor 3 extracts the Bl, B2 and D bits from the signal received by the receiver 32.
8 and input to the frame generation section 40. The frame generation unit 40: (1) sets the 81 bits of the received frame FB to the Bl bit of the frame FA to be transmitted;

■ Set the 82 bits of the received frame FB to the 82 bits of the transmitted frame FA.

■ Set the D bit of the received frame FB to the E bit of the transmitted frame FA.

■ A special pattern (for example, “011111
110'' repeating sequence).

In this way, a new frame FA is generated and sent onto the bus B from the transmitter 33. Note that the numbers ■ to ■ in the figure correspond to the aforementioned processes ■ to ■.

In the terminal device 1, the special pattern in the D bit is detected by the special pattern detection section 14, the switch 12 is switched to the fixed terminal side, and the E bit is supplied to the D channel control section 13. The control unit 13 determines whether the call information included in the E bit is addressed to itself, and if it is addressed to itself, the received Bl
bit and 82 bits are received by the B channel receiving unit 11, and if it is not addressed to the terminal device itself, it is not received as it is addressed to another terminal device. Other operations are similar to those in the relay mode described above.

In this way, in the loopback mode, the 82-bit Bl of the frame FB transmitted from the terminal device 1 is looped back to the 82-bit Bl of the frame FB by the relay/folder device 3. Moreover, it is possible to receive B channel information transmitted by another terminal device 1 in exactly the same way as when communicating with the network terminal device 2.

In the return mode, when a start signal is generated from the network termination device 2 or a communication request from the terminal device 1 to the network termination device 2 is generated (step 40 in FIG. 4), the control section 34 of the relay/return device 3 generates a special pattern generation section 39. (step 41), and after waiting for a certain period of time (step 42), the frame generation unit 4O is stopped and frame transmission to the terminal device 1 is stopped (step 43). Then, switch 35°, 36 and 37 to the fixed terminal a side (step 4).
4) Return to relay mode.

In this case, if the service access point identifier (SAPI) included in the D channel of the frame FB is set to a value that is not used when communicating with the network termination device 2, the communication request from the terminal device 1 to the network termination device 2 can be can be easily detected.

〔Effect of the invention〕

According to the ISDN local communication system according to the present invention, when a terminal device and a network termination device are in a non-communicating state, it is possible to mutually communicate between a plurality of terminal devices without going through the ISDNWI. Since mutual communication is possible on the same interface as when communicating with the ISDN network, there is no need to connect the terminals with a separate interface, and communication with the ISDN network is given priority.
It has the advantage of being able to perform mutual communication without any effect on communication with the DN network, and is highly effective in diversifying communication forms and unifying the communication processes of the communication medium 2 communication means 2.

In addition, during mutual communication, a special pattern is sent out indicating that the callback mode is in effect, so the terminal device can easily identify whether the received signal is from the network terminating device or another terminal device. Communication control can be appropriately managed.

[Brief explanation of the drawing]

Fig. 1 is a principle diagram of the ISDN local communication system according to the present invention, Fig. 2 is a block diagram showing an embodiment of the present invention, and Figs. 3 and 4 are diagrams for explaining the operation of Fig. 2. Flowchart, FIG. 5 is a frame diagram for explaining the operation of FIG. 2, FIG. 6 is a block diagram showing the conventional ISDN communication system, and FIG. 7 is a frame diagram for explaining the operation of FIG. 6. be. 1...Terminal device, 2...Network termination device, 3...Relay/turnback device.

Claims (1)

[Claims] A plurality of terminal devices (1) are connected to a network termination device (2) in a bus wiring format.
), a relay function that relays signals between the terminal device and the network terminating device, and a loopback state for signals received from the terminal device. a callback function that adds a special pattern indicating that the callback is a message and sends it to the terminal device, and switches between the relay function and the callback function by detecting whether or not the terminal device and the network terminating device are in a communication state. Relay with switching function
An ISDN local communication system, characterized in that a return device (3) is provided, and when the terminal device is in a non-communicating state with the network terminal device, mutual communication is performed between the plurality of terminal devices without going through the ISDN network.