JPH0249582B2 - SOJUSHINSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmitting/receiving device, and particularly to a transmitting/receiving device accommodating a plurality of communication terminal devices in a communication network in which a plurality of transmitting/receiving devices share a transmission medium.

As a local communication network installed on a user's premises, communication terminal devices are commonly connected to multiple intermediate taps of coaxial cables via transmitting/receiving devices (transceivers), and each communication terminal device independently transmits information signals. The so-called CSMA/CD method is known, in which transmission is sent to other communication terminal devices, and in the event of a transmission collision between each terminal device, each terminal device stops transmitting and retransmits after a random waiting time. . This coaxial cable is for example
The cable length is about 500m to 2km, and it has a transmission band of about 20MHz, and baseband pulse signals are transmitted. The information to be transmitted includes images, sounds, and data, and is assembled into message blocks such as packets, to which control codes such as destination addresses and check codes are added.

Incidentally, a plurality of communication terminal devices are generally installed at one location within a user's premises. The transceiver is installed very close to the coaxial cable to ensure that the signal on the coaxial cable is within specified conditions, and is connected to a terminal device via an indoor cable from a connector socket placed on the wall of the room. Conventionally, when installing multiple terminal devices in one room, a transceiver was installed on a coaxial cable corresponding to each device, or a collective transceiver was used that included the necessary circuits for each device. The former method increases the number of transceivers installed on the coaxial cable and requires a large installation area. Furthermore, when adding more terminal devices, it is necessary to add more transceivers on the coaxial cable. The latter method simply physically houses each independent transceiver with as many circuits as the number of terminals required in a single housing, requiring a higher component count and therefore being more reliable. It is also space inefficient. Furthermore, even if a transceiver having the necessary number of circuits is initially installed in anticipation of future expansion of the terminal equipment, the initial proportion of the installation will be idle, making it less economical.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate such drawbacks of the prior art and to provide a transmitting/receiving device having a simple and compact device configuration and capable of accommodating a plurality of communication terminal devices.

Another object of the present invention is to provide a transmitting/receiving device that is flexible for increasing the number of communication terminal devices.

Interfacing between a transceiver and a communication terminal device is typically performed under the following conditions. In other words, these conditions include a transmission signal sent from the communication terminal device to the coaxial cable, a reception signal received from the coaxial cable by the communication terminal device, and a collision detection signal that detects a collision of transmissions on the coaxial cable and transmits it to the terminal device. , and power supply. Among these conditions, those other than the transmission signal are signals that are common to all terminal devices and do not depend on individual communication terminal devices. Therefore, the present invention simplifies the configuration of a transceiver by sharing a circuit that handles these common signals with each terminal device accommodated in the transceiver.

According to the invention, the above-mentioned objects are therefore achieved by a transmitting/receiving device as follows. In other words, this transmitting/receiving device includes a transmitting circuit that is provided corresponding to each communication terminal device accommodated therein and transmits an information signal from the communication terminal device to a transmission medium, and a transmitting circuit for each communication terminal device accommodated in this transmitting/receiving device. A single receiving circuit that is provided in common to receive information signals from the transmission medium to each communication terminal device, and a single receiving circuit that is provided in common for each communication terminal device accommodated in this transmitting/receiving device to detect transmission collisions. The device includes a single collision detection circuit for detecting a collision, and a power supply circuit that is provided in common to each communication terminal device housed in the transmitting/receiving device and supplies power to the transmitting circuit, the receiving circuit, and the collision detecting circuit.

Next, embodiments of a transmitting/receiving device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an explanatory diagram showing an embodiment of a local communication network to which a transmitter/receiver according to the present invention is applied. In the figure, both ends 10a and 10b are terminating resistors 12 whose impedances are matched, respectively.
A plurality (n+1) of transmitting/receiving devices (transceivers) 100-0 to 100-n are provided as intermediate taps on the coaxial cable 14 terminated at terminals a and 12b. Each transceiver has connector 10
2, communication terminal devices T00, T01, T10,...
..., Tn0, etc. are connected.

For example, the coaxial cable 14 has a cable length of
It has a transmission band of approximately 20MHz from 500m to 2Km,
It is installed on the premises of the user of this local communication network. The information transferred within the cable 14 is composed of message blocks such as packets, and includes image signals, audio signals, and data signals. Of course, this message block includes control codes such as destination addresses and check codes. Transfer of message blocks occurs in baseband at a rate of 10 megabits/second.

The transceivers 100-0 to 100-n are branch-connected to the coaxial cable 14 with matching impedance at intermediate tap points of the coaxial cable 14, and prevent collisions between transmission and reception of signals between the coaxial cable 14 and the communication terminal devices T00 to Tn0. Performs detection and power supply, etc.

Communication terminal devices T00 to Tn0 are information sources and information sinks such as image terminals, audio terminals, data terminals, or computers, and include interface units with transceivers 100-0 to 100-n.

When transmitting from communication terminal devices T00 to Tn0, a message block containing the destination address is sent to the coaxial cable 14, and each communication terminal device takes in the block when the destination address of the message block matches its own address. . Since there is no control between communication terminal devices, 1
A so-called collision can occur in which one communication terminal starts transmitting almost at the same time as another communication terminal tries to start transmitting immediately thereafter. When a collision occurs, each communication terminal detects this and stops transmitting, and each communication terminal starts transmitting again after a random waiting time has elapsed. This method is called the CSMA/CD method.

FIG. 2 shows the transceiver 100-0 shown in FIG.
100-n. FIG. In FIG. 2, the coaxial cable 14 is branched at an intermediate tap 18, and a branch path 106 connects the transmitting circuit units SB0 to SB3 and the receiving circuit unit.
Connected to RB and collision detection circuit unit CB. Transmission circuit units SB0 to SB3 are transformer 1
08 to the transmitter circuit units SA0 to SA3, both units, e.g. SA0 and SB0.
This constitutes one transmitting circuit. Input 110 of transmitting circuit units SA0 to SA3 is connected to connector 102
is connected to terminal 112 of. The transmitting circuits, for example SA0 and SB0, are circuits that amplify the signal at the input 110, convert its level, and output it to the branch circuit.
Separate the Tn0 side and coaxial cable 14 side by direct current,
In other words, it separates the earth's energy.

In this embodiment, the connector 102 includes terminals 112,
It has four circuits of connector segments 120 including 114, 116, and 118, and is installed in a plug-in socket type at a location within the premises of a user of this local communication network, such as a wall surface of a room where communication terminal devices T00 to Tn0 are installed. It will be arranged in From there, each communication terminal device T00~Tn
0 is connected by a cable 16 with a maximum length of about 50 m. Thus, in this embodiment, the connector 102 corresponding to the transceiver 100-1 is shown in FIG.
Up to four terminal devices T10 to T13 as shown in
Up to one device can be accommodated in each connector segment 120. In this example, as described above,
Transceiver 10 through one connector 102
Although the capacity of communication terminal devices that can be accommodated in 0 is assumed to be 4, this number has no particular significance, and the present invention is not limited to this. The final capacity of the transceiver 100 may be designed taking into consideration the economic efficiency of equipment installation, and any other number may be used.

A receiver circuit unit RB is also connected to the branch path 106, and the receiver circuit unit RB is connected to a receiver circuit unit RA through an earth/air separation transformer 122. Both units RA and RB constitute one receiving circuit, which receives the pulse signal from the coaxial cable 14 through the branch path 106, determines this threshold value, shapes the waveform, converts the signal level, and sends it to the output 124. This is a circuit that gives Output 124 is commonly connected to terminals 114 of all segments 120 of connector 102.

The branch path 106 also includes a collision detection circuit unit.
CB is connected, which is the ground gas separation transformer 126
is connected to the collision detection circuit unit CA by. Both units CA and CB constitute one collision detection circuit, which is connected to any communication terminal device T00 to T00 connected to the coaxial cable 14.
For example, the DC level, that is, the carrier, of the information signal pulse transmitted from Tn0 to the coaxial cable 14 is monitored, and it is detected that the DC level changes significantly when a so-called collision occurs in which two or more terminal devices transmit simultaneously. This is a circuit that detects the occurrence of a collision. Its output 128 is connected to connector 10
It is commonly connected to the terminal 116 of each segment 120 of the two segments. Furthermore, the collision detection circuits CA and CB
may be of a type that detects changes in the frequency of the information signal pulse instead of changes in the DC level.

The transceiver 100 is a DC-DC converter 13
0, which is powered from each terminal device T00-Tn0 via a lead 132 commonly connected to each segment 118 of the connector 102, and
It has a function of supplying DC power to each circuit SB0 to SB3, RB and CB in 00, and also separating the terminal devices T00 to Tn0 side and the coaxial cable 14 side in terms of DC.

These transmitter circuits SA0~SA3 and SB0~
SB3, receiving circuits RA and RB, collision detection circuit CA
, CB, DC-DC converter, etc. are suitable for constructing as a hybrid large-scale integrated circuit (LSI), and this makes it possible to create a small transceiver 10 that can accommodate, for example, about 10 terminal devices.
0 can be achieved.

In normal operation, communication terminal equipment T00~
The information signal sent from Tn0 through the cable 16, terminal 112 and lead 110 is sent to the transmission circuit,
For example, it is amplified by SA0 and SB0 and transmitted from branch path 106 to coaxial cable 14.

For example, if both communication terminal devices T00 and T01 start transmitting almost simultaneously in transceiver 100-0 in FIG. Detects the change and connects both terminal devices T00 and T0 via lead 128.
Notify 1 of the occurrence of a collision. Both terminal devices T00 and T01 stop their transmission, recover, and start transmitting again after a random waiting time.

By the way, the information signals transmitted from other terminal devices T00 to Tn0 to the coaxial cable 14 are sent to the branch path 1.
06 and received by the receiving circuits RA and RB,
The pulse is shaped into a waveform according to the threshold value and output to the lead 124. This connects communication terminal devices T00 to Tn0 through terminal 116 and cable 16.
is input.

Two or more different transceivers 100-0 to 1
Any terminal device T00~ belonging to 00-n
Even if Tn0 starts transmitting almost at the same time,
Collision detection circuit CA of each transceiver as mentioned above
and CB operate to detect a significant increase in the DC level of the signal on the coaxial cable 14, and send the lead 12 to the terminal devices T00 to Tn0 belonging to their respective stations.
8 to notify the occurrence of a collision. The terminal device that caused the collision stops transmitting, and after a random waiting time has elapsed, it restarts and starts transmitting.

The transmitting/receiving device according to the present invention connects a plurality of communication terminal devices installed at the same location on a user's premises, only the transmitting circuit is provided corresponding to each terminal device, and the other circuits are provided in a single common manner. By connecting to a transmitting/receiving device, the configuration of the device is simpler and smaller compared to a transmitting/receiving device that is provided with a transmitting/receiving circuit and a power supply circuit corresponding to each individual terminal device. In addition, the initial equipment is reduced,
There is also flexibility in adding terminal equipment, thus reducing costs and improving reliability.

Although the present invention has been described with reference to a specific embodiment, the present invention is not limited to this. For example, the idea of the present invention can be applied even if the transmission line is an optical transmission line or wireless instead of a coaxial cable. can be realized and achieve the goal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a local communication network to which a transmitting/receiving device according to the present invention is applied, and FIG. 2 is a block diagram showing an embodiment of the transmitting/receiving device according to the present invention. Explanation of symbols of main parts, 14... Coaxial cable, 100... Transmitting/receiving device (transceiver), 1
02...Connector, 108...Transformer, 130...
...DC-DC converter, CA, CB...Collision detection circuit, RA, RB...Reception circuit, SA0, SB0...Transmission circuit, T00...Communication terminal device.

Claims (1)

[Scope of Claims] 1. In a transmitting/receiving device accommodating a plurality of communication terminal devices of a communication network in which a transmission medium is shared by a plurality of transmitting/receiving devices, the transmitting/receiving device has the following functions for each communication terminal device accommodated in the transmitting/receiving device: a transmission circuit that is provided correspondingly and that transmits an information signal from the communication terminal device to the transmission medium; and a transmission circuit that is provided in common to each communication terminal device accommodated in the transmitting/receiving device and that transmits an information signal from the transmission medium to each communication terminal. a single receiving circuit that receives information signals to the device; a single collision detection circuit that is provided in common to each communication terminal device housed in the transmitting/receiving device and detecting a collision between transmissions; A transmitting/receiving device comprising: a power supply circuit that is provided in common to each communication terminal device housed in the device and supplies power to the transmitting circuit, the receiving circuit, and the collision detection circuit.