JPH05336197A - Transmission modem - Google Patents

Abstract

PURPOSE:To secure high transmission reliability by preventing the undesired decrease in a line impedance in the transmission system in which plural MODEMs are not controlled by wastefully connecting between the MODEM circuit and a transmission line in a power supply transient state at the time of rising and falling down of a output signal supplied from the outside of the MODEM. CONSTITUTION:The transmission MODEM intervening between a transmission line and a terminal equipment and used for data transmission is provided with a MODEM circuit 1 performing data modulation and demodulation, a line connection circuit 2 connecting a transmission line 5 and the MODEM circuit 1, a line control circuit 3 connecting the transmission line 5 and the MODEM circuit 1, a line control circuit 3 controlling the transmission reception of data based in the operation of the line connection circuit 2, and power supply control circuit 4 supplying power to work the line connection circuit 2 and blocking the connection of the sender side line immediately when the power supply is unstable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission modem device used for data transmission, and more particularly, to a voice band modem, which transmits data to and from a modem circuit during a power supply transient state of rising and falling of power supplied from outside the modem. The present invention relates to a transmission modem device that blocks unnecessary connection control between roads.

[0002]

2. Description of the Related Art Conventionally, a voice band modem is composed of a modulation / demodulation circuit, a filter circuit, a line interface circuit, a line control circuit, a line connection switch circuit, etc.
As the power supply for operating the line connection switch circuit, the power supply voltage supplied from the outside of the modem is used as it is, or if necessary, it is used via a voltage stabilizing circuit of a predetermined level.

[0003]

According to the above-mentioned prior art, the line control signal input from the outside of the modem or the line in the modem is input during the power supply transient state of rising and falling of the power supplied from the outside of the modem. An undefined state may occur in the control circuit, and if the line connection switch circuit is operable when the power supply voltage for operating the line connection switch circuit is above the specified value in this undefined state, the transmission line and the modem are unnecessary. There was a possibility of controlling the circuit connection.

In the case of a transmission system in which a plurality of modems are connected, when the power supply of the own station modem is applied during the data transmission between the other station modems, if the own station modem circuit is unnecessarily controlled to be connected to the transmission line, the line impedance May occur and a data error may occur due to a decrease in the carrier level, which lowers the transmission reliability of the entire transmission system.

Therefore, according to the present invention, a plurality of modems are connected without unnecessarily controlling the connection between the modem circuit and the transmission line during a power supply transient state at the rise and fall of the power supplied from the outside of the modem. The purpose of the transmission system is to prevent unnecessary reduction of line impedance and ensure high transmission reliability.

[0006]

The present invention will be described with reference to the block diagram shown in FIG.

Transmission data A, which is a logic data signal,
The received data B is input / output to / from the data terminal side, a modem circuit 1 including a modulation / demodulation circuit, a filter circuit and the like, a line connection switch circuit 2 connecting the modem circuit 1 and the transmission line 5, and a line control A transmission modem device equipped with a line control circuit 3 for controlling the line connection switch circuit 2 by a signal C and a power supply control circuit 4 for controlling the supply of externally supplied power D to the line connection switch circuit 2. is there.

[0008]

The modem circuit 1 is a circuit for modulating the transmission data A into a transmission carrier corresponding to the data state and further demodulating the reception carrier into the reception data B corresponding to the carrier state. The line connection switch circuit 2 is a modem circuit. 1 is a switch circuit including a switching element for connecting the transmission line 5 to the transmission line 5, and the line control circuit 3 is a control circuit that controls the line connection switch circuit 2 to NO / OFF according to the state of the line control signal C. The power supply control circuit 4 controls the supply of power to the line connection switch circuit 2 only when the power D supplied from the outside is at a predetermined level or higher, or after applying the power D supplied from the outside for a predetermined time. It is a control circuit that controls the supply of power to the line connection switch circuit 2 after a lapse of time.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the configuration diagram shown in FIG.

Transmission data A, which is a logic data signal,
The received data B is input / output to / from the data terminal side, a modem circuit 1 including a modulation / demodulation circuit, a filter circuit and the like, a line connection switch circuit 2 connecting the modem circuit 1 and the transmission line 5, and a line control A line control circuit 3 for controlling the line connection switch circuit 2 by a signal C and a power supply control circuit 4 for controlling the supply of externally supplied power D to the line connection switch circuit 2 are provided. Power supply control circuit 4
A level detection circuit 4-1 for determining the level of the power supply D supplied from the outside, and a delay circuit 4-2 for delaying the presence detection output of the level detection circuit 4-1 for a predetermined time.
The delay circuit 4-2 is constituted by a transistor 4-3 which is ON / OFF controlled, and the line connection switch circuit 2 is constituted by the transistor 4-3 of the power supply control circuit 4.
The ON / OFF controlled power supply D is input to the relay exciting coil 2-1 as a drive power source, and the relay exciting coil 2-1 outputs ON / OFF by the output of the line control circuit 3.
Relay a contact 2 which is input to the transistor 2-4 controlled to be OFF and whose operation is controlled by the relay exciting coil 2-1
-2 is connected to the transmission line side that connects the modem circuit 1 and the transmission line 5, and the relay b contact 2-3 whose operation is controlled by the relay exciting coil 2-1 is connected to the modem circuit 1 and the transmission line 5. A voice band modem configured to connect to the receiving line side. Next, the operation of this embodiment will be described.

The modem circuit 1 is a circuit that modulates the transmission data A into a transmission carrier corresponding to the data state and further demodulates the reception carrier into reception data corresponding to the carrier state. The transmission carrier is output to the transmission line, The reception carrier is input from the reception line.

The line connection switch circuit 2 is a switch circuit for connecting the modem circuit 1 and the transmission line 5, and the line control circuit 3 turns ON / OFF the line connection switch circuit 2 according to the state of the line control signal C. It is a control circuit that controls
The power supply control circuit 4 is a control circuit that controls the supply of the power D supplied from the outside to the line connection switch circuit 2 as a drive power only when a predetermined condition is satisfied.

The level detection circuit 4-1 in the power supply control circuit 4 is a circuit for determining whether or not the voltage level of the power supply D supplied from the outside is equal to or higher than a preset detection level. The logic "1" is output to the delay circuit 4-2 at the next stage when the voltage level is higher than the detection level and the logic "0" is output below the detection level.

The delay circuit 4-2 is a level detection circuit 4-1.
When the output logic signal is logic "1",
After a preset time delay, the state in which the next stage transistor 4-3 is ON-controlled is output, and the logic "0" is output.
In the case of, the state in which the transistor 4-3 at the next stage is turned off is output instantaneously, and the transistor 4-3 is turned on / off by the output of the delay circuit 4-2. In the on state, the line connection switch circuit 2 to supply power D, O
In the FF state, it operates so that the power supply D is not supplied to the line connection switch circuit 2.

When the line control signal C, which is a logic signal, is a logic "1", the line control circuit 3 outputs a state in which the transistor 2-4 in the line connection switch circuit 2 is ON-controlled, and a logic "0". In this case, the state in which the transistor 2-4 in the line connection switch circuit 2 is turned off is output.

The relay exciting coil 2-1 in the line connection switch circuit 2 is applied with the power supply D controlled by the power supply control circuit 4, and is ON / OFF controlled by a logic signal output from the line control circuit 3. Transistor 2
The excitation is controlled by -4. When the power supply D is supplied from the power supply control circuit 4, the transistor 2-4 is turned on.
In the N state, it is in the excited state and the transistor 2-4 is OF
In the F state, there is no excitation. When the power supply D is not supplied from the power supply control circuit 4, the transistor 2-4
It becomes a non-excitation state regardless of the state of.

The relay a contact 2-2 is a contact for controlling ON / OFF of the transmission circuit connecting the modem circuit 1 and the transmission path 5, and is ON when the relay exciting coil 2-1 is in the excited state.
When the relay exciting coil 2-1 is in the non-excited state, it is turned off.

The relay b contact 2-3 is a contact for controlling ON / OFF of the reception line connecting the modem circuit 1 and the transmission path 5, and is OF when the relay exciting coil 2-1 is in the excited state.
When the relay exciting coil 2-1 is in the non-excited state, the F state is turned on.

That is, when the relay exciting coil 2-1 is in the excited state, the transmission line side is connected between the modem circuit 1 and the transmission path 5, and conversely, when the relay exciting coil 2-1 is in the non-excited state, the modem is connected. As for the connection between the circuit 1 and the transmission line 5, the receiving line side is connected.

The connection between the modem circuit 1 and the transmission line 5 is such that the transmission line side is connected only during transmission and the reception line side is connected except during transmission. In a transmission system in which the transmission line 5 is a non-exchange type and a plurality of modems are connected to the same transmission line, the transmission impedance of the transmission line side of the modem circuit 1 is 600Ω, and the reception impedance of the reception line side is, for example, 10K.
High impedance of Ω or more. This is because a plurality of modems are connected in parallel to the transmission line 5, and the total receiving impedance is brought close to 600Ω. Here, the operating state of each part when the power source D is turned on and off will be described with reference to the operation timing chart of FIG.

The x-axis direction represents time t, and the y-axis direction represents Y.
1 power supply D state, Y2 level detection circuit 4-1 output state, Y
3-transistor 4-3 state, Y4 relay exciting coil 2-
1 power supply state, Y5 transistor 2-4 state, connection state of Y6 modem circuit 1 and transmission line 5.

First, the power supply D supplied from the outside at Y1 rises, and the level detection circuit 4-1 detects the detection level Vp.
Level, the output of the level detection circuit 4-1 indicated by Y2 changes from the logic "0" to the logic "1", and the state of the transistor 4-3 indicated by Y3 changes to the delay circuit 4-2 delay time t.
After d, the OFF state changes to the ON state, and at the same time, the relay excitation coil 2-1 power supply state indicated by Y4 changes from the non-application state to the application state.

Next, the state of the transistor 2-4 indicated by Y5 is indefinite if either the line control signal C or the line control circuit 3 is in an indefinite state from the rise of the power source D to a predetermined level or more and until a predetermined time elapses. State X1 occurs.

However, during this uneasy state X1, the relay exciting coil 2-1 power supply state shown at Y4 is a non-applied state, and the connection state of the modem circuit 1 and the transmission line 5 shown at Y6 is as follows.
Holds the receiving line connection status. After that, if the state of the transistor 2-4 indicated by Y5 changes from the OFF state to the ON state, the connection state of the modem circuit 1 and the transmission line 5 indicated by Y6 changes from the receiving line state to the transmitting line state, and the transistor 2- When 4 changes from the ON state to the OFF state, the transmission line state changes to the reception line state.

Next, when the power supply D indicated by Y1 reaches the falling level detection circuit 4-1 detection level Vp, the output of the level detection circuit 4-1 indicated by Y2 changes from logic "1" to logic "0". At the same time, the state of the transistor 4-3 indicated by Y3 also changes from the ON state to the OFF state, and at the same time, the relay excitation coil 2-1 power state indicated by Y4 also changes from the applied state to the non-applied state.

In the state of the transistor 2-4 indicated by Y5, if any of the line control signal C and the line control circuit 3 becomes indefinite due to the fall of the power supply D, the indefinite state X2 occurs.

However, during the indefinite state X2, the power supply state of the relay exciting coil 2-1 indicated by Y4 is a non-applied state, and the connection state of the modem circuit 1 and the transmission line 5 indicated by Y6 is the reception line connection state. Hold.

In other words, even when either the line control signal C or the line control circuit 3 becomes indefinite during the power supply transient state of rising and falling of the power supply D, the connection state of the modem circuit 1 and the transmission line 5 Can reliably maintain the receiving line connection state.

According to the above-described embodiment, even when an undefined state occurs in the line control operation during the power supply transient state of power supply rise / fall, it is possible to make the transmission line connection state between the modem circuit and the transmission line. In addition, it is possible to prevent unnecessary reduction of the line impedance and ensure high transmission reliability. The present invention is not limited to the embodiments described above, and the following modifications are possible.

(1) As shown in FIG. 4, the transmission line 5 of FIG.
Is a transmission line 5-1 of the transmission side and a transmission line 5-2 of the reception side, and a relay b contact 2 in the line connection switch circuit 2
It is also possible to use a voice band modem on the terminal side corresponding to a 1 to N transmission system that does not require -3.

In this case, the modem circuit 1 is used only when transmitting data.
The transmission line 5-1 and the transmission line 5-1 are connected to each other and the modem circuit 1 and the transmission line 5-1 are controlled so as to be cut off except when data is transmitted. Is 600 Ω during transmission, and is in a high impedance state except during transmission.

Also in the case of this embodiment, as in the case of the above embodiment, even when either the line control signal C or the line control circuit 3 becomes indefinite during the power supply transient state of rising and falling of the power supply D. The connection state between the modem circuit 1 and the transmission side transmission line 5-1 can be maintained in the state of being reliably cut off.

(2) As shown in FIG. 5, the delay circuit 4-2 in the power supply control circuit 4 of FIG. 2 is removed, and the output of the level detection circuit 4-1 is set to the voltage level of the power supply D equal to or higher than the detection level. In this case, the transistor 4-3 can be controlled to be turned on, and when the voltage level of the power supply D is lower than the detection level, the transistor 4-3 can be controlled to be turned off.

In this case, when the indefinite state of the line control operation during the power supply transient state of rising / falling of the power supply D is limited to the range where the voltage level of the power supply D is below a predetermined value, it is shown in FIG. Similar to the embodiment, the modem circuit 1 and the transmission line 5 are operated when the power supply D is in a rising / falling power transient state.
As for the connection state of, the reception line connection state can be surely maintained.

The switching element of the line connection switch circuit 2 is not limited to the relay stored in the embodiment, and a contactless switching element such as an analog switch is naturally included in the present invention.

[0036]

As described above, according to the transmission modem device of the present invention, even when an indefinite state occurs in the line control operation during a power supply transient state of rising and falling of the power supplied from the outside, the modem By forcibly locking the power supply of the line connection switch circuit that connects the circuit and the transmission line, it is possible to prevent changes in the connection state and prevent unnecessary line impedance reduction, and to connect multiple modems High reliability can be ensured in the system.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a transmission modem device of the present invention.

FIG. 2 is a configuration diagram of a transmission modem device according to an embodiment of the present invention.

FIG. 3 is an operation timing chart of the transmission modem device according to the embodiment.

FIG. 4 is a configuration diagram of a transmission modem device according to another embodiment of the present invention.

FIG. 5 is a configuration diagram of a transmission modem device according to another embodiment of the present invention.

[Explanation of symbols]

 A ... Received data B ... Transmitted data C ... Line control signal D ... Power supply 1 ... Modem circuit 2 ... Line connection switch circuit 3 ... Line control circuit 4 ... Power supply control circuit 5 ... Transmission line 2-1 ... Relay excitation coil 2- 2 ... Relay a contact 2-3 ... Relay b contact 2-4 ... Transistor 4-1 ... Level detection circuit 4-2 ... Delay circuit 4-3 ... Transistor 5-1 ... Transmission side transmission line 5-2 ... Reception side transmission Path t ... time td ... delay circuit 4-2 delay time Vp ... level detection circuit 4-1 detection level X1 ... indefinite time X2 ... indefinite time Y1 ... power supply D state Y2 ... level detection circuit 4-1 output state Y3 ... transistor 4 -2 state Y4 ... Relay excitation coil 2-1 power supply state Y5 ... Modem circuit 1 and transmission line 5 connection state

Claims (3)

[Claims] 1. A transmission modem device used for data transmission via a transmission line and a terminal device for modulating data,
A modem circuit for demodulation, a line connection circuit for connecting the transmission line and the modem circuit, a line control circuit for controlling data transmission and reception by the operation of the line connection circuit, and for operating this line connection circuit And a power supply control circuit for blocking the connection of the line on the transmitting side when the power supply is in an indefinite state. 2. The transmission modem device according to claim 1, wherein the transmission modem device is a power supply control circuit having a delay characteristic of delaying a rise of a power supply for a predetermined time. 3. The transmission modem device according to claim 2, wherein the transmission modem device is a power supply control circuit that supplies power only when the level of the power supply is a predetermined value or more.