JPS6267995A - Electronic exchange - Google Patents

Abstract

PURPOSE:To simply and surely prevent the detour of a multifrequency signal by making the multifrequency signal detouring to an exchange circuit through a subscriber's circuit or a trunk circuit further an input line from an outgoing line during outputting the multifrequency signal from a tone generating circuit silent by a silencing circuit. CONSTITUTION:When a multifrequency signal receiver 22 recognizes dial number, a tone generating circuit 21 changes over a selector 27 by a time slot of a trunk line indicated by the dial number and the prescribed dial information is generated and outputted from a tone generating source 26. At this time, a part of the dial information from the tone generating circuit 21 leaks in a hybrid circuit 15 and detours to an input line highway 17. However, in this time slot, a silencing circuit 20 is controlled by a CPU to change over the tone generating circuit 21 and the selector and gives a silent signal from the tone generating source to an exchange circuit 19. As a result, the dial information detoured to the input line highway 17 in the time slot is prevented from passing in the silent circuit 20.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an electronic exchange that can effectively prevent multi-frequency signals from looping around.

[Technical envy of inventions and their problems]

An electronic exchange that receives dial information issued by a subscriber terminal via a switching circuit with a multi-frequency signal receiver, and outputs a multi-frequency signal generated by a tone generation circuit according to the received signal to the central office line as dial information. In this case, there is a problem in that the multi-frequency signal goes around to the multi-frequency signal receiver, causing malfunction of the multi-frequency signal receiver.

That is, as shown in FIG. 3, which schematically shows a signal path for call processing in an electronic exchange, dial information issued by the subscriber terminal 1 is input to the exchange circuit 3 via the hybrid circuit 2. The dial information is then received by the multi-frequency signal receiver 5 via a path 4 formed in the exchange circuit 3, and the dial number is recognized.

In the exchange, dial information corresponding to the recognized dial number is generated from the tone generating circuit 6 and sent to the central office line 8 via the hybrid circuit 1.

Dial tones, busy tones, etc. sent from the central office line 8 are input to the switching circuit 3 via the hybrid circuit 7, and are sent to the hybrid circuit 2 via a path 9 formed in the switching circuit 4. is output to the subscriber terminal 1.

However, in the hybrid circuit 2.7, there is mismatch due to variations in line impedance, etc., and the occurrence of signal leakage due to this is undeniable. Therefore, the dial information (multi-frequency signal) output from the tone generation circuit 6 mixes into the path 9 of the exchange circuit 3 via the hybrid circuit 7,
The signal is output to the subscriber terminal 1 via the hybrid circuit 2.

Furthermore, the dial information output to this subscriber terminal 1 is
It mixes into the path 4 of the switching circuit 3 via the hybrid circuit 2.

As a result, the dial information generated by the tone generating circuit 6 is mixed into the dial information from the subscriber terminal 1 that is provided to the multi-frequency signal receiving circuit 5 via the path 4, and the multi-frequency signal receiving circuit 5 This causes a problem in that the dial information cannot be recognized correctly.

Therefore, in conventional exchanges, a measure has been taken in which the path 9 in the switching circuit 3 is cut off when dialing information is sent to the central office line 8, thereby preventing the detour.

By the way, in recent electronic exchanges, as the scale of the exchanges has increased (the number of lines handled has increased), the control of the central office line circuit and the exchange circuit 4 has been controlled using multiple CPUs due to the limit of the exchange processing capacity of one CPU. We are trying to perform decentralized control.

In such a distributed control type electronic exchange, the CP
Due to the delay in transmitting information between U stations, it is very difficult to send dial information to the office line 8 and disconnect the path 9 at the same time. In other words, after it is detected that the dial information has been sent to the office line 8, the path 9 is controlled to be disconnected after a detection time delay.

During the period of such control delay (time difference), it is not possible to prevent the dial information from being passed around. For this reason, multiple C
In electronic exchanges using a distributed control system using PUs, it has not been possible to solve the problem of erroneous detection of multifrequency signals.

[Summary of the invention]

The present invention has been made in consideration of these circumstances, and its purpose is to provide an electronic exchange with high operational reliability that can easily and reliably prevent the looping of multi-frequency signals. It is in.

[Summary of the invention]

The present invention generates a multi-frequency signal on the outgoing side of a switching circuit formed by connecting subscriber circuits and trunk circuits via incoming lines and outgoing lines, and transmits the multi-frequency signal to the subscriber circuit or trunk circuit via the outgoing lines. a tone generation circuit for outputting to the switching circuit, and a silencing circuit capable of silencing a multi-frequency signal input to the switching circuit via the input line on the input line side of the switching circuit; When the multi-frequency signal is output, the multi-frequency signal that passes from the outgoing line through the subscriber circuit or the trunk circuit and further through the incoming line to the exchange circuit is muted by the muting circuit. be.

In other words, the multi-frequency signal is time-divisionally exchanged in the exchange circuit, and the mute circuit mutes the multi-frequency signal input to the exchange circuit in the time slot in which the tone generating circuit generates the multi-frequency signal.

〔Effect of the invention〕

Thus, according to the invention, separately from the control of the switching circuit,
In synchronization with the transmission of the dial information (multi-frequency signal) by the tone generation circuit, the dial information that is to be input into the exchange circuit by loopback can be muted. Therefore, even if the path is still formed in the switching circuit,
Since the dial information from the tone generation circuit due to wraparound is only muted and output to the subscriber terminal, even if the muted signal mixes with the dial information from the subscriber terminal, it will not have an adverse effect.

As a result, the multifrequency signal receiver can always correctly receive dial information from subscriber terminals and recognize it.

Furthermore, the above-mentioned mute control can be performed in complete synchronization with the dial information generation control by the tone generation circuit, so that effects such as being able to easily and reliably prevent dial information from being passed around can be achieved. be given

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an electronic exchange according to an embodiment.

In FIG. 1, 11 is a subscriber circuit including a hybrid circuit 12, and a subscriber terminal 13 is connected to this subscriber circuit 11. In FIG. Further, 14 is a trunk circuit (office line circuit) including a hybrid circuit 15, and an office line 16 is connected to this trunk circuit 14.

Although a plurality of each of the subscriber circuits 11 and trunk circuits 14 are actually provided, only one necessary for the explanation of the operation is shown here.

Thus, subscriber circuit 11 and trunk circuit 14 are connected to incoming highway 17 and outgoing highway 18, respectively. The incoming highway 17 transfers signals from the subscriber circuit 11 and the trunk circuit 14 to the time-sharing switching circuit 19 via a muting circuit 20 connected to the incoming side of the time-sharing switching circuit 19.

The outgoing highway 18 also transfers the signal exchanged and controlled by the time division exchange circuit 19 to the subscriber circuit 11 and the trunk circuit 14, and further to the multifrequency signal receiver 22 via the tone generation circuit 21. be.

The CPU 23 controls the switching operation of the time division switching circuit 19 and its call processing.
24 is the above-mentioned silencing circuit 20 and tone generating circuit 21
It controls the operation of peripheral circuits including The control operation is received by the multi-frequency signal receiver 22,
It is controlled by various recognized signals.

As shown in FIG. 2, the tone generation circuit 21 includes, for example, a tone generator wA 26 that generates various tone signals, and a tone signal generated by the tone signal generation source 26 or outputted by the time division switching circuit 19. and a selector 27 that selectively outputs signals to the outgoing highway 18. The CPU 24 controls the operation of the selector 27 and the type of tone signal generated by the tone generation source 26.

Further, the silence circuit 20 is essentially constructed in the same manner as the tone generation circuit 21 described above, but a selector selects a signal from the incoming highway 17 or a silence signal generated by a tone generation source. , is different in that this is output to the time division exchange circuit 19.

This silence signal is realized by repeating a specific PCM code, for example. Specifically, if you follow A-LAW'
10000000'' is realized as a null code, and according to μmLAW, it is realized as a code of ``11111111''.

In the electronic exchange configured as described above, when dial information is issued from the subscriber terminal 13, the dial information is transmitted from the subscriber circuit 11 to the incoming highway 17 in the time slot assigned to the subscriber circuit, and then silently. The signal is input to the switching circuit 19 via the switching circuit 20. Exchange circuit 1
At 9, this dial information is outputted to the multi-frequency signal receiver 22 in the allocated time slot, and the information is outputted to the outgoing highway 18 via the tone generation circuit 21. As a result, the multi-frequency signal receiver 22 receives the dial information and recognizes the dial number.

When the multi-frequency signal receiver 22 recognizes the dial number, the CPU 24 operates according to the recognition result, and under the control of the CPU 24, the tone generating circuit 21 switches the selector 27 at the time slot of the office line indicated by the dial number. ,
Predetermined dial information is generated and output from the tone generation source 26. As a result, the dial information is the outgoing highway 18.
The signal is transferred to the trunk circuit 14 via the central office line 16, and output to the central office line 16.

At this time, part of the dial information from the tone generating circuit 21 leaks through the hybrid circuit 15 and goes around to the incoming highway 17. However, in this time slot, the mute circuit 20 switches the selector at the same time as the 1.-tone generating circuit 21 under the control of the CPU 24, and the mute signal from the tone generator is transferred to the switching circuit. 1
It is given to 9.

As a result, the dial information from the tone generation circuit 21 that has entered the incoming highway 17 in the above time slot is as follows.
The silencing circuit 20 stops the passage of the signal. In this implementation order, the silencing circuit 2o and the tone generating circuit 21 are mutually synchronously controlled by the same CPU 24. As a result, the above-described control is performed in a completely synchronized state, and the dial information is replaced by a mute signal in the mute circuit 20.

However, at this time, the switching circuit 19 forms a path for exchanging time slots in order to output the dial tone and busy tone from the central office line 16 to the subscriber terminal 13. However, when the dial information is output from the tone generator 21, the selector of the mute circuit 20 is switched from the input highway 17, so the signal outputted to the subscriber terminal 13 via the path is only the mute signal. becomes.

Therefore, even if this mute signal goes around to the incoming highway 17 via the hybrid circuit 12 of the subscriber circuit 11, the DC level of the dial information from the subscriber terminal 13, for example, changes only slightly. Therefore, the multi-frequency signal receiver 22 is able to reliably recognize the dial information, and no problems like those of the prior art occur.

In this way, in this system, the 1-tone generation circuit 21 and the silence circuit 20 are completely synchronized by the control system of the peripheral circuit independently of the call processing and line connection control tIl system. can be used to control its operation. Further, without cutting the path formed in the exchange circuit 19, it is possible to completely block the looping of the dial information output from the 1-to-1 line generation circuit 21 to the subscriber circuit 11.

In addition, the looping of dial information is prevented only by the switching control of the selector, and there is no need for path disconnection control in the exchange circuit 19, so the control processing can be simplified and the control operation can be ensured. The effect is produced.

Note that the present invention is not limited to the embodiments described above. Here, an example is given of an electronic exchange that is controlled in a distributed manner using a plurality of CPUs, but the present invention can be similarly applied to an electronic exchange that is centrally controlled by one CPU. Further, the silent signal may be generated by blocking the signal from the incoming highway 17 with a selector and setting the output of the selector to zero level. In this case, the silencing circuit 20 can be realized by a switch, and the silencing circuit 20 having the configuration shown in FIG. 2 described above can be omitted. In addition, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an electronic exchange according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of the configuration of a tone generation circuit and a silencing circuit in the embodiment, and FIG. FIG. 3 is a diagram showing a signal path for call processing. 11... subscriber circuit, 12... hybrid circuit,
13...Subscriber terminal, 14...Trunk circuit, 15
...Hybrid circuit, 16...Station line, 17...
Incoming highway, 18 Outgoing highway, 19... Time division switching circuit, 20... Silencing circuit, 21... Tone generation circuit, 22... Multifrequency signal receiver, 23, 24.
...cpu.

Claims (2)

[Claims] (1) In an electronic exchange in which subscriber circuits and trunk circuits are connected to a switching circuit via incoming and outgoing lines, the switching circuit is provided on the outgoing side of the switching circuit and generates a multi-frequency signal to connect the outgoing line. a tone generating circuit that outputs to the subscriber circuit or trunk circuit via the input line; and a tone generator provided on the incoming line side of the switching circuit, which is capable of silencing the multi-frequency signal input to the switching circuit via the incoming line. when the tone generating circuit outputs the multi-frequency signal, the multi-frequency signal flowing from the outgoing line through the subscriber circuit or the trunk circuit and further via the incoming line to the exchange circuit is converted into the silent mode. An electronic switching system characterized by being silent in a switching circuit. (2) The switching circuit performs time-division switching, and the silencing circuit mutes the multi-frequency signal input into the time slot in which the tone generating circuit generates the multi-frequency signal. Electronic switching equipment according to scope 1.