JPS6317388B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a line switching device, and more particularly to a switching device between a leased line and a subscriber telephone line in data communications.

Data communications, including facsimile communications, include dedicated communications between specific subscribers using dedicated lines set up by business entities and companies, and communications between unspecified subscribers using subscriber telephone lines (public communication lines). There is a subscription communication that takes place between the parties. When using subscriber telephone lines, various technical standards have been established to prevent interference with telephone and other communications.
When connecting a converter to a subscriber's telephone line and switching between a data terminal and this telephone, if the data terminal is installed on your own, you are required to connect a line protection device PD.

There are two types of dedicated lines for data transmission: long-distance dedicated lines and local dedicated lines.With local dedicated lines, direct DC signal transmission is possible, but high-speed transmission causes a lot of noise. , transmitted as an alternating current signal using a modem. For long-distance dedicated lines,
In order to prevent signal attenuation, an amplifier is provided along the way, and a modulation/demodulation device is used to transmit the signal as an alternating current signal.

For example, connecting a facsimile device to a local telephone line to transmit facsimile signals typically involves
A set consisting of a facsimile control unit, a communication control unit (CCU), a modulation/demodulation unit (MODEM), and a network control unit (NCU) is connected to the subscriber telephone line. The communication control unit provides an interface with the data line, converts serial bit strings on the data line to serial/parallel, performs data signal rate matching, performs error checking, detects and inserts control codes, and performs connection confirmation and termination. Perform transmission control functions such as In addition, the subscriber telephone line network control device performs connection control of the subscriber telephone exchange network, that is, activation of the central office exchange,
In addition to performing restoration, sending selection signals, detecting calling signals, etc., this device also has functions such as switching to a data communication path and maintaining a loop.

In addition, in order to connect the same facsimile device to a dedicated line and transmit facsimile signals, it is not possible to connect the subscriber telephone line set as is, and instead of the network control unit (NCU), the dedicated line connection control, In other words, it is necessary to connect a line control unit (LCU) that has functions such as sending a selection signal, detecting a ringing signal, switching to a data communication path, and switching to a leased line telephone, and this must be built into the set. Must be.

On the other hand, in a facsimile for a subscriber telephone line that has a network control unit (NCU), the method of switching the line to a dedicated line is as shown in Figure 1. When connecting to the network control unit (NCU) in the facsimile, as shown in Figure 2,
data from the modem and the modem.
There are cases where the line is switched and connected between the subscriber telephone line and the leased line using an external switching device. That is, the first
In the figure, in a facsimile device 10, a facsimile control section 5 is connected to a subscriber telephone line LN via a communication control section 4, a modem switching control section 3, a modem device 2, and a network control device 1. Dedicated line
Connection with the PL is made via an external modulation/demodulation device 6, and line switching is performed by switching between the built-in modulation/demodulation device 2 and the external modulation/demodulation device 6 in the modem switching control section 3. Switching control is performed manually when transmitting, and for incoming calls from the dedicated line PL,
Automatically switches depending on the code signal. In addition, for incoming calls from the subscriber telephone line LN, the network control device 1
Received by this phone connected to.

However, with the switching method shown in Figure 1, the dedicated line PL
When switching to the other side, an external modulation/demodulation device 6 is required, which increases the cost accordingly. In addition, dedicated line PL
Although analog signals are transmitted from the modem to the modem 6, digital signals are transmitted at the interface between the modem 6 and the facsimile device 10, so voice communication cannot be performed over a dedicated line in this state. Usually, a time division device (TDM) is inserted after the modem 6 and a digital telephone is used to make calls.

The facsimile device 10 shown in FIG. 1 is a modified facsimile device for subscriber telephone lines, and a printed board of the modem switching control section 3 is inserted into the facsimile device 10.
It is also necessary to change the input/output wiring between the modem 2 and the communication control section 4. If possible, it is desirable to use the facsimile equipment for subscriber lines as is.

Next, in FIG. 2, between the back of the network control device 1, that is, between the network control device 1 and the modem device 2, the data line from the modem device 2 is connected to the subscriber telephone line LN and the leased line by an external switching device 8. Switch and connect the PL. This switching method is mainly used to switch between the subscriber telephone line LN and the international digital line PL, using a manual switch in the external switching device 8,
It is connected to the international digital line via a 2-wire to 4-wire conversion hybrid coil 18, a facsimile signal level adjustment unit 9 for transmitting to the international digital line, and an international digital adapter 11. Further, an automatic facsimile receiving unit 12 is provided for converting a call into a digital signal and displaying the incoming call on the facsimile control unit 5 when a call is received via the international digital line.

However, this facsimile automatic receiving unit 12
Unless the switch in the switching device 8 is manually switched to the dedicated line side, the facsimile device 10' cannot be brought into the receiving state.
When the switch is not switched to the leased line side, the operator of the facsimile machine 10' accepts incoming calls from the international line using the handset connected to the international data adapter 11, and the operator switches the switch on the panel to the leased line side. , press the receive button on the facsimile to enter reception mode.

By combining three automatic facsimile reception units 12, signal level adjustment units 9, and switching devices 8,
It has become one set.

In this way, in the switching method shown in Fig. 2, the subscriber telephone line and the dedicated line are switched at the rear of the network control device 1, so the network control device 1 cannot be shared, and an external signal level adjustment unit is installed. 9 and a device 12 for activating reception of the facsimile device, the cost is high. Furthermore, line switching during reception is not performed automatically, which is extremely inconvenient.

An object of the present invention is to eliminate such drawbacks, and when switching and connecting a subscriber telephone line and a dedicated line, to share the network control device for the subscriber telephone line when connecting the leased line, and to manually transmit and receive data. To provide a line switching device that can sometimes automatically switch lines and reduce costs and simplify operations without modifying a subscriber telephone line data terminal device (for example, a facsimile device).

In order to achieve the above object, the line switching device of the present invention is added to a subscriber telephone line data terminal device having a network control device, and is connected to the subscriber telephone line and the leased line. The direct current circuit on the line side of the device has means for switching and connecting the subscriber telephone line and the dedicated line, and the AC circuit on the data terminal side of the network control device has an attenuator for adjusting the signal level sent to the subscriber telephone line. , when connecting a line protection device and a disconnector to a dedicated line, the above-mentioned attenuator, line protection device, and disconnector are short-circuited and routed through an attenuator, etc. for the dedicated line. .

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a system diagram when a facsimile device is switched and connected to a two-wire or four-wire dedicated line using the present invention, and FIG. FIG. 2 is a system diagram when a facsimile device is switched and connected.

In the line switching device of the present invention, the interface of the dedicated line connection section differs depending on the form of the dedicated line.
In FIG. 3, a facsimile device 20 is connected to a connection point of a two- or four-line dedicated line PL via a line switching device 30 of the present invention, and the line switching device 30 switches and connects it to a subscriber telephone line LN. The facsimile device 20 for the subscriber telephone line can be connected to the dedicated line PL without any modification. Line switching device 30
The main telephone 13, which accepts incoming calls on the subscriber telephone line LN while communicating with the leased line PL, and the subscriber telephone line LN
A dedicated line telephone 14 is connected which responds by voice to an incoming call on the dedicated line PL during communication with the private line PL. Note that an attached telephone 7 is connected to the network control device within the facsimile device 20.

Figure 4 shows a case where the private branch exchanges 16 are connected using a private toll line PLN, and dial pulses are transmitted in-band (in-band frequencies 1900 to 2400).
An in-band ringer 17 is inserted into the leased line.

Of course, in the case of a local dedicated line, in-band
Ringer 17 is not necessary. When the facsimile device 20 is connected only to the private line PLN via the extension telephone of the private branch exchange 16, the facsimile device 20 is directly connected to the extension telephone. On the other hand, when the subscriber telephone line LN and the private line PLN are switched and connected, the facsimile device 20 is connected to the extension telephone via the line switching device 40 of the present invention. It is also connected to the subscriber's telephone line LN via the line switching device 40. Note that 15 is an extension telephone.

FIG. 5 is a detailed configuration diagram of the line switching device shown in FIG. 3.

The subscriber telephone line LN is usually connected to a line switching device 30.
The network control device 1 of the facsimile device 20 via
connected to. Facsimile communication on the subscriber telephone line LN is performed by a subscriber telephone line facsimile device 20 incorporating a normal MA type (manual transmission, automatic reception) network control device 1 for both transmission and reception. Even if the line switching device 30 malfunctions or the power is cut off, the subscriber's telephone line LN and the facsimile device 20 are connected at the normal contact side of the relay contacts ns and y, so facsimile communication is possible. be. facsimile device 20
From the PD terminal, that is, the data output side of the modem 2, to the attenuator 26 and the disconnector 2 in the line switching device 30.
1. Since it is connected to the PD terminal of the facsimile device 20, that is, the data input side of the network control device, via the line protection device (PD) 19, the existing terminal of the facsimile device 20 can be used, and the facsimile device 20 No modification is necessary. The transmission level of the signal sent to the subscriber telephone line LN is
It is adjusted by an attenuator 26.

Next, when transmitting to the dedicated lines PL4W and PL2W, the dedicated line selection switch 25 of the line switching device 30
By operating the sequence control circuit 32
to operate relays Y and NS. Contact point y
is switched, the line switching device 30 is switched from the modem 2 to the line switching device 30.
The attenuator 26, the separator 21, and the protector 19 inside are released and connected to the network control device 1 through a direct path that short-circuits them, and further connects to the network control device 1, and other contacts y and relay K.
2, contact x, hybrid coil H, transmission amplifier 39, dedicated line attenuator 28, 4-wire separator 2
7, and is connected to the 4-wire dedicated line PL4W via the line protection device 22. In that case, the transmission level is adjusted by attenuator 28. In addition, the 2-wire signal is transmitted via the transmission amplifier 39, the hybrid coil H, the 2-wire separator 23, and the line protection device 24.
Connected to dedicated line PL2W. The transmission level at this time is corrected by adjusting the gain of the transmission amplifier 39 to compensate for the transmission level attenuated by the hybrid H, and is adjusted by the dedicated line attenuator 28 to match the line conditions of the dedicated line. . In this way, a call to the 4-line or 2-line opposing leased line terminal is initiated. In this case, line switching device 3
0 is the subscriber telephone line even when connected to a leased line.
The same interface conditions as LN are given to the facsimile device 20.

When contact ns is switched by the operation of relay NS, subscriber telephone line LN is switched to main telephone 13, and in response to an incoming call from subscriber telephone line LN, main telephone 1 is switched.
3. Respond with voice. Calls between subscriber telephone line LN and this telephone 13 are monitored by relay K1,
On the other hand, communication between the dedicated line PL and the facsimile device 20 is monitored by the relay K2. Fax machine 2
When the communication of 0 ends, relay K2 detects this and opens contact k2, and sequence control circuit 32 detects this and restores relays Y and NS.
This opens contacts y and ns to connect the subscriber telephone line.
LN and the facsimile device 20 are connected and the normal state returns, but if the relay K1 is operating at that time, the contact k1 remains closed, so the sequence control circuit 32 maintains the operation of the relay NS.
Secure a call using this telephone 13.

Next, when an incoming call is received from the leased line PL, the detector 29 detects the calling signal (two-wave frequency signal) from the opposing leased line terminal via the receiving amplifier 41, so the relay is relayed under the control of the sequence control circuit 32. Operate Y and NS, and fax machine 2
0 from the subscriber's telephone line LN to the dedicated line PL. That is, the contact y of the DC circuit at the front of the network control device 1 switches and connects both lines, and the contact y of the AC circuit between the modem 2 and the network control device 1 allows attenuation to be performed in the same way as during transmission. Vessel 2
6. Disconnect the disconnector 21 and line protection device 19,
Forms a short circuit path. After the connection, relay SG2 is operated to send a 16 Hz calling signal from oscillator 31 to facsimile device 20, thereby causing facsimile device 20 to enter a receiving state.

After connecting to the dedicated line PL and immediately before starting communication, relay CA is activated to close contact ca and form a reception path. Furthermore, when a call is received on the dedicated line PL while the facsimile device 20 is communicating with the subscriber telephone line LN, the sequence control circuit 32 activates the relay SG1.
to call the dedicated line telephone 14. When the leased line operator off-hooks, the relay L detects this and drives the sequence control circuit 32, operating the relay X to close the contact x and causing a voice response to be made to the opposing leased line. Also,
When the facsimile device 20 receives a call from the leased line PL while it is communicating with the subscriber telephone line LN and the operator is absent, the sequence control circuit 3
2 detects the signal from the detector 29 and the closing of the contact k1 of the monitoring relay K1, operates the relay SG3, closes the contact sg3, and sends a busy tone from the signal generation circuit 38 to the dedicated line PL. You can also do it. Also,
The signal generation circuit 38 generates a selection signal and sends it to the private line PL when calling. Note that the 16 Hz calling signal is sent to either the dedicated line telephone 14 or the facsimile device 20 by operating either relay SG1 or SG2.

In this way, by using the line switching device 30 of FIG. 5, the network control device 1 with built-in facsimile
can be shared by the subscriber telephone line LN and the dedicated line PL, so there is no need to improve the facsimile equipment for the subscriber telephone line. In addition, subscriber telephone line
Level adjustment during transmission to LN and dedicated line PL is performed by separate attenuators 26 and 28, and line protection device 1
9, 22, 24 and cutters 21, 24, 27
They can also be connected separately according to standards. Note that the dotted connection lines of Hybrid H are points that are separated or connected during construction or delivery testing.

FIG. 6 is a detailed configuration diagram of the line switching device shown in FIG. 4.

In this case as well, the subscriber telephone line LN is normally connected to the facsimile device 20 via the line switching device 40.
network control device 1. Subscription telephone line
The path for communicating with LN is exactly the same as in FIG.

Next, the leased line side (the extension of the private branch exchange, hereinafter referred to as
When transmitting via a PBX extension (hereinafter referred to as PBX extension), first operate the changeover switch 25 to drive the sequence control circuit 33 to operate the relay Y1, switch the contact _Y1 , and switch the facsimile device 20 to the dedicated line PL. Connect to. That is, the line is switched and connected by contact _y1 of the DC circuit at the front of the network control device 1, and the PD terminal of the facsimile device 20,
That is, an attenuator 26, a divider 21, and a line protection device (PD) connected to the AC circuit on the data output side of the modem 2 and the data input side of the network control device 1.
19 is separated by contact y ₁ , and the attenuator 3 for the dedicated line is connected.
7. Switch and connect the disconnector 36 and line protection device 35 to the connected path. However, in this case,
In the case of a local leased line, the short-circuit path is separated by an X mark so that the signal is transmitted via an attenuator 37 and a separator 36 that adjust the transmission level to the leased line, and a line protection device 35. Construction will be carried out so that signals can be transmitted via the short circuit path without having to disconnect at the X mark when using a dedicated long-distance line. In the case of a dedicated long-distance line, level adjustment and line protection are performed within the in-band ringer 17 shown in Figure 4.
It is not required on the extension side.

After the facsimile device 20 is connected to the PBX extension, the attached telephone 7 confirms the dial tone of the PBX extension, performs a dial operation, and calls the terminal on the opposite dedicated line. After the PBX sends a ring tone,
Communication begins when connected to the other party.

During communication with the PBX extension, contact ns is switched by the operation of relay NS, so that subscriber telephone line LN is connected to main telephone set 14, and incoming calls from subscriber telephone line LN are answered with voice by main telephone set 14.

As in the case of FIG. 5, communications with the leased line are monitored by relay K2, and calls with subscriber telephone line LN are monitored by relay K1. When communication with the leased line ends, relay K2 detects this, and sequence control circuit 33 restores relay Y1 and switches and connects facsimile device 20 to subscriber telephone line LN, but relay K1 detects that a call is in progress. Relay NS will not be restored while

Next, when a call is received from the dedicated line side (PBX extension), the ringing detection circuit 34 detects the 16Hz ringing signal sent to the PBX extension. Here, no ring trip is performed, but the relay Y1 is operated under the control of the sequence control circuit 33, and the facsimile device 20 is switched and connected from the subscriber telephone line LN to the dedicated line through the contact _y1 . After switching and connecting, the 16Hz calling signal from the PBX extension is sent to the facsimile device 20 as is. As a result, the facsimile device 20 shifts to a receiving state.
In addition, in the same way as when transmitting, the relay NS operates to switch the contact point NS, and when there is an incoming call from the subscriber telephone line LN, the telephone 14 makes a voice response. Also, relay K1 performs busy monitoring on the subscriber telephone line side, and relay K2 performs busy monitoring on the leased line side.

In addition, if the facsimile device 20 is connected to a subscriber telephone line
When a call is received on the PBX extension while communicating with LN, the sequence control circuit 33 detects that communication is in progress by operating relay K1, operates relay Y2, switches contact _y2 , and calls the extension telephone 15. Give a voice response.

As explained above, according to the present invention, line switching between the leased line and subscriber telephone line is performed by the line-side DC circuit which is the front part of the network control device, so that the network control device for the subscriber telephone line is It can also be used for lines, and lines can be switched without any modification to data terminal equipment such as facsimile machines. Furthermore, by using the line switching device of the present invention, a dedicated line connection can have the same interface conditions as a subscriber telephone line, and line selection at the time of transmission can be performed manually, while switching at the time of reception can be performed automatically. Moreover, even if the line switching device fails or the power is cut off, communication is always possible because it is based on the subscriber telephone line connection. Note that the present invention is not limited to facsimile, but can also be applied to general data communication.

[Brief explanation of the drawing]

1 and 2 are block diagrams showing a conventional line switching method, FIG. 3 is a block diagram showing a first embodiment of a line switching device of the present invention, and FIG. 4 is a block diagram of a line switching device of the present invention. A block diagram showing the second embodiment, FIG. 5 is a detailed configuration diagram of the line switching device of FIG. 3, and FIG. 6 is a detailed configuration diagram of the line switching device of FIG. 4. 1: Network control device, 2: Modulation/demodulation device, 5: Facsimile control unit, 7: Attached telephone, 13: Subscriber telephone line main telephone, 14: Leased line telephone, 15: Extension telephone, 16: Private branch exchange, 17: In-band・
Ringer, 19, 22, 24, 35: Line protection device, 20: Facsimile device, 21, 23, 2
7, 36: Separator, 26, 28, 37: Attenuator, 29: Ringing signal detector, 30, 40: Line switching device, 31: 16Hz signal generator, 32, 33:
Sequence control circuit, 34: Ringing detection circuit, 38: Selection signal, busy signal generator, 39, 4
1: Transmission and reception amplifier.

Claims (1)

[Scope of Claims] 1. In a line switching device added to a subscriber telephone line data terminal device having a network control device and connected to the subscriber telephone line and a leased line, a direct current circuit on the line side of the network control device is provided. , has means for switching and connecting the subscriber telephone line and the leased line, and includes an attenuator for adjusting the signal level sent to the subscriber telephone line, a line protection device, and a disconnector in the AC circuit on the data terminal side of the network control device. 2. A line switching device characterized in that when connecting a line to a leased line, the attenuator, the line protection device, and the disconnector are short-circuited and the line is routed through the attenuator for the leased line. 2. The line switching device according to claim 1, wherein the means for switching and connecting the subscriber telephone line and the leased line is such that the network control device is normally connected to the subscriber telephone line. 3. The means for switching and connecting the subscriber telephone line and the leased line is characterized in that the subscriber telephone line is switched and connected to the telephone set at the same time as the subscriber telephone line is switched and connected to the leased line, so that incoming calls from the subscriber telephone line are answered by voice. A line switching device according to claim 1. 4. The above means for switching and connecting the subscriber telephone line and the leased line constantly monitors communication between the subscriber telephone line and the leased line, and as long as it detects that communication is in progress, switching is not performed even if other communications are terminated. 2. The line switching device according to claim 1, wherein the line switching device is not connected.