JP4091776B2 - Line terminal equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a facsimile apparatus and the telephone or the like, relate to the line terminal equipment of the communication device.
[0002]
[Prior art]
According to the European standard TBR21 for telephone line terminals, (1) the period of 400mS immediately after the line loop is created must not be less than the standard current, (2) the standard current is within 7mS immediately after the line loop is created. Standards such as (3) maintaining the current of the standard value for 1200 mS or less immediately after the circuit loop is created are defined. In the prior art, the DC loop resistance is decreased immediately after the circuit loop is formed, and at the same time, the AC resistance is increased to satisfy the above standard.
[0003]
[Problems to be solved by the invention]
By the way, the conventional techniques as described above have the following problems to be solved. A large change in direct current generated immediately after the circuit loop is created adversely affects the function of increasing the AC resistance, and the excessive response generated at that time sometimes deviates from the standard.
[0004]
[Means for Solving the Problems]
The present invention adopts the following configuration in order to solve the above points.
<Configuration 1>
A line loop connected in parallel between the line and the communication device and receiving a direct current from the line and informing the line side of the connection with the communication device; and reducing the direct current resistance of the line loop to reduce the direct current A line terminal device comprising an impedance control means that facilitates acceptance and prevents an inflow of a communication signal to the line loop by increasing an AC resistance of the line loop, and a modem that performs communication , The impedance control means includes an opening / closing means for reducing the AC resistance when open and preventing generation of an excessive response current when receiving the DC current, and accepting the DC current from the line by opening the opening / closing means. At the same time, after the DC current is received and a predetermined time elapses and before the communication by the modem is started, the switching means is closed and the AC resistance is closed. Line Terminal apparatus characterized by increasing.
[0005]
<Configuration 2>
In the line terminal device according to Configuration 1, the impedance control means includes a collector-grounded transistor amplifier and a capacitor that extends from the base of the transistor amplifier to the ground through the switching means, and the collector grounding is performed when the switching means is open. The output resistance of the type transistor amplifier becomes the DC resistance, and when the switching means is closed, the transistor amplifier becomes the base-grounded amplifier for the communication signal, and the output resistance of the base-grounded amplifier becomes the AC resistance. A characteristic line terminal device.
[0006]
<Configuration 3>
A line loop connected in parallel between the line and the communication device and receiving a direct current from the line and informing the line side of the connection with the communication device; and reducing the direct current resistance of the line loop to reduce the direct current Impedance control means for facilitating acceptance and preventing the inflow of communication signals to the line loop by increasing the AC resistance of the line loop; and mute means for bypassing the impedance control means and receiving the DC current; A line terminal device including a modem that performs communication, and when the DC current is accepted, the mute means bypasses the impedance control means to prevent the generation of a transient response current when the DC current is accepted, and the DC current is accepted. After a predetermined time has passed and before the modem starts communication, the mute means is stopped and Line Terminal apparatus characterized by an active impedance control means.
[0009]
<Action>
The impedance control means includes an opening / closing means for opening / closing the AC resistance increasing function, and when the circuit loop is formed, the opening / closing means is opened, and the opening / closing means is opened after a predetermined time has elapsed after the DC resistance is reduced. The AC resistance increasing function is functioned by closing. In this way, a large change in direct current that occurs immediately after the formation of the line loop reduces the adverse effect on the AC resistance increasing function, thereby satisfying the standard.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described using specific examples.
<Specific example 1>
FIG. 1 is a circuit configuration diagram of the line terminal device of the first specific example.
[0011]
As shown in FIG. 1, the line terminal device 1 of the first specific example includes a line switching means 2, a DC cut means 3, a communication transformer 4, a line matching means 5, a level switching means 6, a rectifier diode bridge 7, a line protection means 8, and a line loop. An ON-OFF means 9, an impedance control means 10, a mute means 11, a constant current means 12, an opening / closing means 13 and a capacitor 14 are provided.
[0012]
The line switching means 2 is disposed at a position closest to the line on the signal line connecting a line (including an exchange) (not shown) and the modem 16 (communication equipment) via the line connection terminal 19, and the line and the line terminal device. 1 is a switch for connecting and releasing 1. In the ON-HOOK (standby state), it is connected to the terminal c, and in the OFF-HOOK (communication state), it is connected to b. These ON-OFF controls are performed by the CPU 17 via the I / O port 15.
[0013]
The direct current cut means 3 is arranged on the signal line connecting the line and the modem 16 after the line switching means 2 and the rectifier diode bridge 7 described later, and the direct current fed from the line is applied to the communication transformer 4 described later. It is a capacitor that prevents flow.
[0014]
The communication transformer 4 is a part arranged after the DC cut means 3 on a signal line connecting the line and the modem 16 to connect a communication signal (AC signal including a control signal) between the line and the modem 16.
[0015]
The line matching means 5 is a part arranged on the modem 16 side of the communication transformer 4 on a signal line connecting the line and the modem 16 to match the line and the modem 16.
The level switching means 6 is a part arranged on the modem 16 side of the communication transformer 4 on the signal line connecting the line and the modem 16 to switch the signal level.
[0016]
The rectifier diode bridge 7 is arranged in parallel between the line switching means 2 and the DC cut means 3 on the signal line connecting the line and the modem 16, and serves as a direct current supplied from the line as an entrance to a line loop described later. Etc. are taken into the line loop.
[0017]
Here, the line loop is a loop that passes through the rectifier diode bridge 7 → line loop ON / OFF means 9 → impedance control means 10 (parallel mute means 11) → constant current means 12 → rectifier diode bridge 7 and communicates with the line. A loop circuit that is connected in parallel with a device (such as the modem 16) and receives a direct current from the line and informs the line side of the connection with the communication device.
[0018]
For example, when an abnormal voltage such as induced lightning occurs on the line and a high voltage is applied to the line terminal device 1, the line protection unit 8 short-circuits the signal line to the line terminal device 1 or subsequent communication equipment. This is a protective element for preventing high voltage intrusion.
[0019]
The line loop ON / OFF means 9 is a part that forms the line loop when turned on by the control of the CPU 17 via the I / O port 15 and extinguishes the line loop when turned off. Usually, a switching element using a combination of a photocoupler and a phototransistor is used.
[0020]
The impedance control means 10 is disposed after the line loop ON / OFF means 9 in the line loop, reduces the DC resistance of the line loop to facilitate the reception of the DC current, and the AC resistance of the line loop. This is a part for preventing the inflow of communication signals to the line loop.
[0021]
The impedance control means 10 comprises a collector-grounded transistor amplifier, and includes a capacitor 14 that extends from the base of the transistor amplifier to the ground via an opening / closing means 13. When the open / close means 13 is opened, the output resistance of the collector grounded transistor amplifier becomes the DC resistance. Since the capacitor 14 is connected between the base of the transistor Tr and the ground when the switching means 13 is closed, the transistor amplifier functions as a base-grounded amplifier for the communication signal. The output resistance of the grounded base amplifier is the AC resistance. Opening / closing of the opening / closing means 13 is controlled by the CPU 17 via the I / O port 15.
[0022]
That is, it is configured to function as a grounded collector transistor amplifier having a low output resistance for a DC signal and to function as a grounded transistor amplifier having a high output resistance for an AC signal. In this way, the line loop can easily accept a direct current from the line, and a communication signal can be prevented from flowing into the line loop.
[0023]
The mute means 11 is a part of the line loop that is arranged in parallel with the impedance control means 10 after the line loop ON / OFF means 9 and has a function of operating or stopping the impedance control means 10. For example, when a dial pulse is transmitted, the function of the impedance control means 10 is temporarily interrupted to prevent erroneous recognition of the exchange. These operations are controlled by the CPU 17 via the I / O port 15. Usually, a switching element using a combination of a photocoupler and a phototransistor is used.
[0024]
The constant current means 12 is a part that causes a predetermined constant current to flow through the line loop when the line loop is formed so that the presence of the communication device is recognized on the line side.
[0025]
<Operation of Specific Example 1>
FIG. 2 is an operation flowchart of the first specific example.
The operation of the first specific example will be described with reference to FIG.
[0026]
S1
The CPU 17 connects the line switching unit 2 ab via the I / O port 15. A predetermined DC voltage is applied to the signal line connecting the line and the modem 16 from the line side.
[0027]
S2
The CPU 17 turns on the line loop ON / OFF means 9 via the I / O port 15. A line loop is formed, and a direct current is supplied from the line side, and a predetermined constant current is passed to the line side through the rectifier diode bridge 7 → line loop ON-OFF means 9 → constant current means 12 → rectifier diode bridge 7. Return. At this time, the mute means 11 remains in the OFF state. Further, the opening / closing means 13 remains open, and the capacitor 14 is not yet connected to the impedance control means 10. Accordingly, since the impedance control means 10 operates as a grounded collector amplifier, the DC resistance of the line loop is reduced.
[0028]
S3
The CPU 17 sets the timer to 3 seconds after turning on the line loop ON-OFF means 9. The current status is maintained until this timer times out.
[0029]
S4
The CPU 17 closes the opening / closing means 13 via the I / O port 15 after the timer times out. In this state, the capacitor 14 is connected between the base of the transistor Tr1 of the impedance control means 10 and the ground. Accordingly, the impedance control means 10 operates as a base-grounded amplifier for AC signals. As a result, the AC resistance of the line loop increases, so that communication signals can be prevented from flowing into the line loop.
[0030]
S5
The same state continues during the ON-HOOK state.
S6
When changing from the ON-HOOK state to the OFF-HOOK state, the CPU 17 switches the line loop ON-OFF means to OFF via the I / O port 15.
[0031]
S7
The CPU 17 switches the line switching unit to OFF via the I / O port 15. At that time, the opening / closing means 13 is also switched to the open state. Thus, the operation of the specific example 1 is completed.
[0032]
In the control method of the first specific example, as described in S2 above, when the line loop is formed, the opening / closing means 13 is still open, and 3 seconds after the line loop ON-OFF means 9 is turned on. The content is switched to the connection state, and this content will be described in detail with reference to other drawings.
[0033]
FIG. 3 is an explanatory diagram of the amount of change in the conventional line loop current.
FIG. 3 shows the amount of change in the line loop current when the function of decreasing the DC resistance of the line loop and the function of increasing the AC resistance are simultaneously performed immediately after the line loop is formed. That is, this corresponds to the case where the line loop ON / OFF means 9 (FIG. 1) is switched ON while the open / close means 13 of the impedance control means 10 (FIG. 1) is closed.
[0034]
The vertical axis represents the current flowing through the line loop, and the horizontal axis represents time.
When the line loop ON / OFF means 9 (FIG. 1) is switched ON at time T1, a line loop is formed, and a predetermined amount of direct current is applied to the rectifier diode bridge 7 → line loop ON / OFF means 9 → constant current means 12 → It flows through the rectifier diode bridge 7 and exceeds the standard value in the figure.
[0035]
However, since the switching means 13 (FIG. 1) remains closed at this time, a transient response current flows through the capacitor 14 (FIG. 1). This transient response current may be added to the constant current and deviate from the standard. The standard deviation range surrounded by a circle in the figure represents this state. After the transient response is over, a predetermined constant current value is obtained at time T2.
[0036]
On the other hand, in the specific example 1, at the time T1 when the line loop is formed, the switching means 13 (FIG. 1) is still open and the capacitor 14 (FIG. 1) is not connected. That is, after the line loop is formed, the switching means 13 (FIG. 1) is closed after a predetermined time has elapsed, and the AC resistance is increased. Therefore, the transient response current in the vicinity of time T1 falls within a negligible range. In S4, the switching means 13 (FIG. 1) is closed 3 seconds after the formation of the line loop, but even if a transient response current is generated at this time, it is already out of the standard range, and thus there is no problem.
[0037]
<Effect of specific example 1>
As described above, the impedance control means 10 (FIG. 1) is provided with the opening / closing means 13, and when the circuit loop is formed, the opening / closing means 13 is kept open, and after the DC resistance is reduced, the opening / closing means 13 is opened. By closing the means 13 and causing the AC resistance increasing function to function, a large change in direct current generated immediately after the formation of the line loop reduces the adverse effect on the AC resistance increasing function, and the required standard. Satisfied.
[0038]
<Specific example 2>
FIG. 4 is a circuit configuration diagram of the line terminal device according to the second specific example.
From FIG. 4, the line terminal device 21 of the specific example 2 includes a line switching means 2, a DC cut means 3, a communication transformer 4, a line matching means 5, a level switching means 6, a rectifier diode bridge 7, a line protection means 8, and a line loop. An ON-OFF means 9, an impedance control means 22, a mute means 11, a constant current means 12, and a capacitor 14 are provided.
[0039]
Differences from the line terminal device 1 (FIG. 1) of the specific example 1 are as follows. The line terminal device 1 (FIG. 1) of the first specific example includes an impedance control means 10 (FIG. 1), a capacitor 14 (FIG. 1) via a switching means 13 (FIG. 1) between the transistor Tr1 (FIG. 1) and the ground. Is arranged. That is, the capacitor 14 (FIG. 1) is connected or disconnected between the transistor Tr1 (FIG. 1) and the ground by opening / closing the opening / closing means 13 (FIG. 1). On the other hand, in the impedance control means 22 provided in the line terminal device 21 of the specific example 2, the capacitor 14 is directly disposed between the transistor Tr1 and the ground. Since the configuration of the other parts is exactly the same as the line terminal device 1 of the first specific example and the line terminal device 21 of the second specific example, the description is omitted.
[0040]
<Operation of Specific Example 2>
FIG. 5 is an operation flowchart of the second specific example.
The operation of the specific example 2 will be described according to the steps in FIG. 5 with reference to FIG.
[0041]
P1
The CPU 17 connects the line switching unit 2 ab via the I / O port 15. A predetermined DC voltage is applied to the signal line connecting the line and the modem 16 from the line side.
P2
The CPU 17 turns on the mute means 11 via the I / O port 15.
[0042]
P3
The CPU 17 turns on the line loop ON / OFF means 9 via the I / O port 15. A line loop is formed, and a direct current is supplied from the line side. The rectifier diode bridge 7 → line loop ON-OFF means 9 → mute means 11 → constant current means 12 → rectified diode bridge 7 is passed through the rectifier diode bridge 7 to the line side. Return as current. At this time, since the mute means 11 is ON, the impedance control means 22 is stopped.
[0043]
P4
The CPU 17 sets the timer to 3 seconds after turning on the line loop ON-OFF means 9. The current status is maintained until this timer times out.
[0044]
P5
The CPU 17 turns off the mute means 11 via the I / O port 15. When the mute means 11 is turned off, the impedance control means 22 operates. The line loop is changed from rectifier diode bridge 7 → line loop ON-OFF means 9 → impedance control means 22 → constant current means 12 → rectifier diode bridge 7. Accordingly, the impedance control means 22 operates as a collector grounded amplifier for a direct current and operates as a base grounded amplifier for an AC signal. As a result, it becomes easy to accept a direct current into the line loop and to prevent a communication signal from flowing into the line loop.
[0045]
P6
The same state continues during the ON-HOOK state.
P7
When changing from the ON-HOOK state to the OFF-HOOK state, the CPU 17 switches the line loop ON-OFF means to OFF via the I / O port 15.
[0046]
P8
The CPU 17 switches the line switching unit 2 to ac through the I / O port 15. Thus, the operation of the specific example 2 is completed.
[0047]
In the control method of the specific example 2, as described in P3 above, when the line loop is formed, the mute means 11 (FIG. 4) is turned on and the impedance control means 22 (FIG. 4) is stopped. After 3 seconds at P5, the mute means 11 (FIG. 4) is turned off and the impedance control means 22 (FIG. 4) is activated. This will be described in detail with reference to other drawings.
[0048]
FIG. 6 is an explanatory diagram of a change amount of the line loop current in the second specific example.
The vertical axis represents the current flowing through the line loop, and the horizontal axis represents time.
The muting means 11 (FIG. 4) is already turned on before the line loop ON-OFF means 9 (FIG. 4) is switched ON at time T1. Therefore, even if the ON-OFF means 9 (FIG. 4) is switched to ON, the impedance control means 22 (FIG. 4) is stopped.
[0049]
Therefore, at time t1, a loop circuit of rectifier diode bridge 7 → line loop ON-OFF means 9 → mute means 11 → constant current means 12 → rectifier diode bridge 7 is formed, and a predetermined constant current flows suddenly. A transient response current due to the capacitor 14 (FIG. 4) is not generated. In this state, the loop current exceeds the standard value.
[0050]
However, in this state, the impedance control means 22 (FIG. 4) does not play the original role of preventing the inflow of communication signals by increasing the AC resistance. Therefore, the mute circuit is turned off at time t2 after 3 seconds from time t1, and the impedance control means 22 (FIG. 4) is activated.
[0051]
At this time, a transient response current caused by the capacitor 14 (FIG. 4) flows and the line loop current becomes below the standard value (circle in the figure). However, since this time t2 is already outside the standard range, there is no problem. Furthermore, since the impedance control means 22 (FIG. 4) is activated after a short time (3 seconds) after the formation of the line loop to prevent the inflow of communication signals, no particular problem occurs.
[0052]
<Effect of specific example 2>
By adopting the above-described line control method, the mute means is turned on immediately before the line loop is formed, and the mute means is turned off after a predetermined time has elapsed after the line loop is formed. It is possible to meet the required standards without any changes.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram of a line terminal device according to a specific example 1;
FIG. 2 is an operation flowchart of a specific example 1;
FIG. 3 is an explanatory diagram of a change amount of a conventional line loop current.
FIG. 4 is a circuit configuration diagram of a line terminal device according to a specific example 2;
FIG. 5 is an operation flowchart of a specific example 2;
6 is an explanatory diagram of a change amount of a line loop current in Example 2. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Line terminal device 2 Line switching means 3 DC cut means 4 Communication transformer 5 Line matching means 6 Level switching means 7 Rectifier diode bridge 8 Line protection means 9 Line loop ON / OFF means 10 Impedance control means 11 Mute means 12 Constant current means 13 Switching means 14 Capacitor 15 I / O port 16 Modem 17 CPU
18 ROM / RAM
19 Line connection terminal

Claims (3)

A line loop connected in parallel between the line and the communication device and receiving a direct current from the line and informing the line side of the connection to the communication device; and reducing the direct current resistance of the line loop to reduce the direct current A line terminal device comprising: impedance control means for facilitating acceptance and preventing an inflow of a communication signal into the line loop by increasing an AC resistance of the line loop ; and a modem for performing communication ,
The impedance control means includes an opening / closing means for reducing the alternating current resistance when open and preventing generation of an excessive response current when the direct current is received,
The open / close means is opened to receive a DC current from the line, and after the DC current is received and a predetermined time elapses, and before the start of communication by the modem, the open / close means is closed to reduce the AC resistance. A line terminal device characterized by being increased . The line terminal device according to claim 1,
The impedance control means includes
A collector grounded transistor amplifier and a capacitor connected from the base of the transistor amplifier to the ground via the switching means, and when the switching means is opened, the output resistance of the collector grounded transistor amplifier becomes the DC resistance, When closed, the transistor amplifier becomes a grounded base amplifier for the communication signal, and the output resistance of the grounded base amplifier becomes the AC resistance. A line loop connected in parallel between the line and the communication device and receiving a direct current from the line and informing the line side of the connection with the communication device; and reducing the direct current resistance of the line loop to reduce the direct current Impedance control means for facilitating acceptance and increasing the AC resistance of the line loop to prevent communication signals from flowing into the line loop; and mute means for bypassing the impedance control means and receiving the DC current; A line terminal device including a modem for communication,
At the time of receiving DC current, the impedance control means is bypassed by the mute means to prevent generation of transient response current at the time of receiving DC current,
A line terminal apparatus characterized in that the mute means is stopped and the impedance control means is enabled after a predetermined time has elapsed after receiving a direct current and before the communication by the modem is started.

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