JPH0546732B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a control method for a multi-drop leased line.

[Background of the invention]

A multi-drop dedicated line has N branches,
In each branch, it refers to a dedicated line that is capable of receiving signals sent from other (N-1) branches and transmitting signals to other (N-1) branches.

Figure 1 shows the principle of signal reception and transmission in one branch. (a) shows the relationship between the multidrop terminal MD and each signal line, and (b) shows the relationship between the multidrop terminal MD and each signal line.
This figure shows the internal structure of .

Here, the multi-drop terminal MD is composed of output two-branch amplifiers DA1-DA3 and two-input amplifiers MA1-MA3.

In Figure 1b, the signal from incoming line A is DA
1. It is transmitted to the outgoing line C via MA2. Similarly, a signal from incoming line D is transmitted to outgoing line B via DA2 and MA1.

On the other hand, the outputs of DA1 and DA2 are branched from the above route and transmitted to E via MA3. E becomes the receiving terminal at this branch point.

In addition, the signal from F is branched into two at DA3 and sent via MA1 and MA2 to output lines B and C, respectively.
can be conveyed to. F becomes the transmission terminal at this branch point.

FIG. 2 shows an example of a network in which branch terminals MD1 to MD4 of multi-drop dedicated lines are connected to exchanges EX1 to EX4.

Generally speaking, in a multi-drop private line, certain branches are used for transmission, and the others are used only for reception.

In this case, there was a problem in that it was extremely difficult to sort out competition and it was difficult for each exchange to perform both transmission and reception on an equal footing as shown in Figure 2.

[Purpose of the invention]

The purpose of the present invention is to solve the above-mentioned problems in a system in which there are multiple branch points for transmitting and receiving, and each branch point is equal, and to provide a control method for a multi-drop dedicated line that does not conflict with each other. Our goal is to provide the following.

[Summary of the invention]

The present invention attempts to solve the above problems by providing a signal channel for sending control signals from one station to other (N-1) stations.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

FIG. 3 is a system configuration diagram showing an embodiment of the multi-drop leased line control method according to the present invention. In FIG. 3, the multi-drop leased line is an M line, and the branch point is 4. (However, this number of branch points is not necessarily 4.) Then, correspondingly, the multi-drop terminals MD11 to
1M, ~MD41~4M are installed. Furthermore, exchanges EX1 to EX4 are installed corresponding to each branch point. Each exchange EX1 to EX4 is provided with signal transmitters/receivers SR1 to SR4, and each signal transmitter/receiver
SR1 to SR4 are connected by four signal channels. Focusing on one signal channel, as shown in FIG. 3B, one station is transmitting S, and the others are receiving R.

Although this signal channel itself can be called a multi-drop system, contention is avoided by limiting transmission to one.

Next, we will explain how to control the connection of a multi-drop dedicated line using this signal channel.

There are M dedicated lines 1 to M that connect the stations EX1 to EX4. If we do not decide which of M to use, the selection itself becomes a conflict. Therefore, one station (for example, EX1) is designated as the master station. This master station performs all selection and allocation of dedicated lines. Each station is
A command for selecting a dedicated line is sent to the master station via a signal path, and the master station instructs the specific station to allocate a specific dedicated line using the same command. The specific station can exclusively use the dedicated line until it applies to the master station for release of the dedicated line allocation using the same procedure. The specific station sends connection control commands to other stations regarding this dedicated line, and each station sends commands such as responses thereto.

In this way, connection control using the dedicated line is performed without any contention between the stations.

As described above, according to the present invention, N stations can stand on completely equal footing and can control a multi-drop dedicated line without contention.

In the embodiment described above, four dedicated lines are used for control. In such a case, a method is known in which a part of the frequency band above the audio channel is used as a signal channel.

FIG. 4 shows a block diagram of a signaling device for this purpose. In FIG. 4, LPF is a low-pass filter, MOD is a modulator, BPF is a band-pass filter, HYB is a hybrid transformer, and DEM is a demodulator. According to the CCITT standard, if the upper limit of audio is cut off at 2.1KHz using a low-pass filter LPF, four 100 baud signal paths can be created above it. This signal path can be associated with the four signal paths described in FIG.

In this way, there is no need to use a dedicated signal dedicated line, and an economical multi-drop dedicated line control system can be constructed.

〔Effect of the invention〕

According to the present invention, it is possible to realize a multi-drop leased line control system in which any station can take the initiative and there is no mutual competition, and broadcast communication can be performed economically.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the operating principle of a multi-drop dedicated line, FIG. 2 is a system configuration diagram using a conventional multi-drop dedicated line, and FIG. 3 is a system configuration diagram showing an embodiment of the control method according to the present invention. FIG. 4 is a block diagram of a signaling device for passing a control signal through a part of the audio channel. DA1~DA3...Output 2 branch amplifier, MA1~
MA3...2-input amplifier, MD...multidrop terminal, EX...exchange, SR...signal transmitter/receiver,
LPF...Low pass filter, MOD...Modulator, BPF
…bandpass filter, HYB…hybrid transformer, DEM…demodulator.

Claims (1)

[Claims] 1 A control method for a multi-drop dedicated line in a system in which a multi-drop dedicated line having N branches is used and N stations are interconnected, wherein N signal channels are connected to the N stations. For each station, only the other (N
-1) Send signals to each station, and select any one station among the N stations as a multi-drop dedicated line;
As the allocation authority that makes the allocation, before each station other than the allocation authority uses the multi-drop dedicated line, the station allocates the use of the multi-drop leased line to the above-mentioned allocation authority via the signal channel corresponding to the station. A control method for a multi-drop leased line, characterized in that the usage allocation authority grants permission to use a specific leased line to the station making the allocation request, thereby controlling whether or not the multi-drop leased line can be used. . 2. The control method for a multi-drop leased line according to claim 1, wherein a control channel obtained by frequency-dividing the multi-drop leased line itself to be controlled is used as the signal channel.