JP2002247616A - Line terminator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a line terminator that can prevent occurrence of noises due to a difference of current consumption between transmission and reception. SOLUTION: When a N(normal)/R(reverse) control section 105 turns a N/R switch 109 to a reverse state ('H'), the line terminator reaches communication state with a subscriber, when a transmission reception control section 104 brings a reception section 103 to an operating state ('H'), an 'L' output of a NAND circuit 110 turns on a transistor(TR) 111, that causes a current to flow via a variable resistor 112. Furthermore, the reception section 103 uses an AGC(automatic gain controller) switch 114 to select the resistance of the variable resistor 112, so that the difference from the current consumption between the transmission and reception states, depending on the resistance of a line before the communication with the subscriber. Thus, smoothing of the difference from the current consumption between the transmission and reception states different from each line can prevent the occurrence of noises.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line terminating device, and more particularly to a line terminating device which repeats transmission and reception in a predetermined cycle in a time-division manner and performs bidirectional communication with a subscriber via a line.

[0002]

2. Description of the Related Art Conventionally, ISDN (Integrated)
Services Digital Network)
The ping-pong transmission method has a mechanism in which bidirectional communication is performed by repeating transmission and reception at a cycle of 400 Hz, and the load difference between transmission and reception is large. The current consumption fluctuated greatly. In addition, since a plurality of ISDN line packages are accommodated in the same line termination device, and all ISDN lines repeat transmission and reception at the same cycle, the above-mentioned fluctuation in current consumption is superimposed and increased with an increase in the number of ISDN lines. I was

In the ISDN line, data is converted into a digital signal and transmitted and received at the same cycle.
Although the fluctuation of the current consumption is small on the line itself, the analog line mixed in the same line terminating device as the ISDN line package always transmits and receives regardless of the cycle of the ISDN line. For this reason, power supply noise is generated due to the fluctuation of the current consumption, and is mixed into an analog line during communication as noise of 400 Hz which is an audible band. In order to prevent this, some improvements have been made by changing the power supply of the line terminating equipment to a large capacity or changing the power supply wiring connected to each package for the ISDN line to a low impedance one. .

[0004]

However, in order to prevent the above-mentioned power supply noise, some improvement can be achieved by increasing the capacity of the power supply of the line terminating device and reducing the impedance of the power supply wiring. Since it is necessary to temporarily stop the operation of the terminating device and then change the internal structure, there is a problem that it takes enormous cost and time to implement the above measures in all the line terminating devices.

[0005] In addition, I
Since all the packages for the SDN line repeat transmission and reception at the same cycle, the power supply noise is superimposed and increased with an increase in the number of accommodated ISDN lines, and thus the number of accommodated lines is limited.

Further, since the line length and diameter of the line differ for each subscriber, the line resistance from the subscriber to the line terminating device is not constant, and when the line resistance is large, the consumption between transmission and reception is large. When the difference in current is small, and conversely when the line resistance is small, the difference in current consumption between transmission and reception is large. Therefore, in order to flatten the difference in current consumption between transmission and reception in order to prevent power supply noise, it is necessary to consider the difference in line resistance up to the subscriber.

Therefore, the present invention has been made to solve the problems of the prior art, and has as its object the difference between the current consumption at the time of transmission and that at the time of reception, and the difference of each subscriber line. It is an object of the present invention to provide an excellent line terminating device that prevents the occurrence of power supply noise by flattening a difference in current consumption between transmission and reception due to a difference in line resistance.

[0008]

According to the present invention, a line terminating device connected to a subscriber via a line, repeats transmission and reception in a predetermined cycle in a time-division manner, and performs bidirectional communication with the subscriber. And a current correction unit for increasing current consumption at the time of reception and correcting a difference from current consumption at the time of transmission, and performing on / off control of the current correction unit in response to the cycle. A line termination device is obtained.

The current correction means is controlled to be turned on during the reception, and is controlled to be turned off during the transmission. The current correction means is adapted to supply a correction current during reception. It is characterized by including a variable resistor and a selection means for selecting a resistance value of the variable resistor.

[0010] Further, prior to communication with the subscriber, means for detecting the line resistance of the line in advance is further included, and the resistance value is selected according to the detection result.

The operation of the present invention will be described. When transitioning to the communication state with the subscriber, the transmission / reception control unit controls the transmission unit and the reception unit to the respective operation states at a cycle of 400 Hz. However, when the reception unit is in the operation state, the transmission and reception from the variable resistor toward the ground is performed. A current flows so as to correct the difference from the current consumption. Also,
Prior to communication with the subscriber, the optimal resistance value of the variable resistor that flattens the difference in current consumption between transmission and reception according to the line resistance of the line is selected. Current flows from the resistor to ground. This allows
The difference in current consumption between transmission and reception, which differs for each line, is completely flattened, thereby preventing the occurrence of noise mixed in an analog line mounted on the same device.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a configuration of a line termination device according to an embodiment of the present invention. In FIG. 1, a line terminating apparatus according to the present invention includes a transformer 108 for generating and outputting a ping-pong transmission pulse to a subscriber on the transmitting side, and a switch for intermittently connecting both ends of the primary side of the transformer 108 to the ground. (Hereinafter, referred to as “SW”) 106 and 107 and SW1
06 and 107 that operate alternately.

Next, the receiving side is a transformer 108 for receiving a ping-pong reception pulse from the subscriber, and a + side divided on the basis of an AG (analog ground) connected to the middle point of the primary side of the transformer 108. The receiving unit 103 detects the ping-pong pulse (PP) and the negative ping-pong pulse (PM). Further, the transmission / reception control unit 104 includes the transmission unit 1
02 and the receiving unit 103 are alternately operated at a cycle of 400 Hz. An N (normal) / R (reverse) switch 109 is connected between the line terminating device and the subscriber via the line 113.
The N / R control unit 105 sets the N / R switch 109 to the reverse state when communicating with the subscriber, and sets the N / R switch 109 to the normal state during standby.

Further, the power supply module unit 101 converts the input -48 V power supply (not shown) into a +5 V power supply,
5V power is supplied to each block in the line termination device.
The current correction circuit 100 includes a NAND circuit 110,
A transistor 111 and an AGC (Automatic
It comprises a Gain Control switch 114 and a variable resistor 112, and one of the variable resistors 112 is connected to the ground. The N / R control unit 105 sets the N / R switch 109 to the reverse state, and the transmission control unit 10
4, the current correction circuit 100 operates when the receiving unit 103 is in the operating state, and a current flows from the variable resistor 112 selected by the AGC switch 114 to the ground.

Further, the receiving unit 103 performs a training operation prior to the line connection with the subscriber, calculates a line resistance determined based on the line length and the line diameter of the line 113, and performs transmission and reception between the transmission and reception corresponding to the line resistance. In order to eliminate the difference in current consumption (hereinafter, this current is referred to as “correction current”), AGC
The resistance value of the variable resistor 112 is selected by the switch 114.

Next, the operation of the line terminal according to the embodiment of the present invention will be described in detail. In FIG. 1, when shifting from the standby state to the communication state with the subscriber, first, the output signal from the N / R control unit 105 is set to “H”, so that the N / R switch 109 is set to the reverse state.

At the time of transmission, the transmission / reception control unit 104 transmits
02 is operated, and the receiving unit 103 is stopped. Transmission unit 1
02, when the + side waveform is generated, the transmitting unit 10
The SW 106 is operated by a PP (Pinpump Plus) terminal 2 to connect one of the primary sides of the transformer 108 to the ground, generate a positive waveform on the secondary side of the transformer 108, and connect the line through the N / R switch 109. Output to 113.

To generate a negative waveform, the PM1 (ping-pong minus) terminal of the transmitting unit 102 is used to generate SW1.
07, the other side of the primary side of the transformer 108 is connected to the ground, and a current is caused to flow in the opposite direction to the above-mentioned + waveform to generate a −waveform on the secondary side of the transformer 108.
Output to the line 113 through the / R switch 109.

As described above, at the time of transmission, one of the transformers 108
Because of the structure in which + 5V connected to the middle point on the next side is grounded to the ground, it is necessary to supply a large current from the power supply module unit 101 to the transformer. At this time, the operation of the current correction circuit 100 is controlled by the N / R control unit 105.
Is “H” and the output of the transmission / reception control unit 104 is “L” with respect to the reception unit 103.
The output of 10 becomes “H” and the transistor 111 which is turned on by “L” is turned off, so that the power of +5 V is not supplied to the variable resistor 112.

On the other hand, at the time of reception, the transmission / reception control unit 104 stops the transmission unit 102 and operates the reception unit 103. If the received signal from the subscriber has a positive waveform, the N / R switch 10
9, the voltage of + polarity input to the secondary side of the transformer 108 is connected to the middle point of the primary side receiving winding.
Since a positive voltage is generated with respect to G, the receiving unit 103
Is input to the PP terminal. When the signal received from the subscriber has a negative waveform, the transformer 10
The negative polarity voltage input to the secondary side of No. 8 generates a negative side voltage with respect to AG connected to the middle point of the primary side receiving winding. Is input to

As described above, at the time of reception, one of the transformers 108
Since the + waveform and the − waveform are determined and input to the receiving unit 103 with reference to the AG at the middle point on the next side, little power is required for driving the transformer 108 from the power supply module unit 101 and the receiving unit 103 Only a small amount of current to be consumed.

At this time, the operation of the current correction circuit 100 is N
Since the output of the / R control unit 105 becomes “H” and the output of the transmission / reception control unit 104 also becomes “H” with respect to the receiving unit 103, the output of the NAND circuit 110 becomes “L” and “L”.
, The transistor 111 which is turned on is turned on, so that the power of +5 V is supplied to the variable resistor 112. Thus, A
Since the correction current flows through the variable resistor 112 selected by the GC switch 114, the current consumption is flattened.

Next, in the training operation when the receiving unit 103 shifts to the line connection state with the subscriber, the line 1
A method of calculating the line resistance of No. 13 will be described. FIG.
5 is a diagram illustrating an operation of calculating a line resistance by an AGC (not shown) in the receiving unit 103 according to the present invention. In FIG. 2, the received signal level (S) from the subscriber input to the PP terminal or the PM terminal of the receiving unit 103 is compared with the level obtained in the AGC setting step (15 steps in total). AGC when two levels are almost equal
The line resistance is calculated from the number of steps.

First, in FIG. 2A, the AGC 8 step level is lower than the S level.
The number of AGC steps is increased to (c). FIG.
In FIG. 2C, since the AGC 12 step level has exceeded the S level, the number of steps is reduced by one in FIG. 2D. As a result, in FIG.
The eleven step levels are almost equal.

Here, the line resistance of the subscriber line is 81 at the maximum.
Since it is 0Ω, the line resistance at this time is 810Ω × 11
/ 15 = 594Ω (about 600Ω),
The AGC switch 114 is set with the number of AGC steps 11 at this time. That is, the AGCO
AGC8, AG of AGC switch 114 from UT terminal
A control signal for turning on C2 and AGC1 is output, and the resistance of the variable resistor 112 is selected by these switches. This makes it possible to obtain a correction current corresponding to a change in current consumption at the time of transmission due to a difference in line resistance for each line, so that the difference in current consumption between transmission and reception can be completely flattened.

By the way, when the failure location of the line termination device is specified and the internal inspection of the line termination device is performed,
Set the line termination device to the loopback test status.
This loopback test is performed by setting the output signal from the N / R control unit 105 to “L”, thereby setting the N / R switch 1
09 is set to the normal state. The transmission / reception control unit 1
04 causes both the transmitting unit 102 and the receiving unit 103 to operate. The pulse waveform generated by the transmitting unit 102 is
08 is excited and also input to the receiving side,
The signal is input to the PP terminal or the PM terminal of the receiving unit 103. Thus, during the loopback test, the transmission unit 10
2 and the receiving unit 103 operate at the same time, so that the current consumption does not fluctuate.

At this time, the operation of the current correction circuit 100 is such that the output of the transmission / reception control unit 104 is "H" for the reception unit 103.
However, since the output of the N / R control unit 105 is “L”, the output of the NAND circuit 110 is “H” and “L”.
, The transistor 111 that is turned on is turned off, so that the power of +5 V is not supplied to the variable resistor 112.

FIG. 3 shows the relationship between the operating state of the line termination device and the current consumption when the current correction circuit according to the present invention is added. FIG. 4 shows the relationship between the operation state of the conventional line termination device and the current consumption. As shown in FIG. 4, in the conventional line termination device, there was a difference in current consumption between transmission and reception, so that noise was always generated during communication. On the other hand, according to the present invention, as shown in FIG. 3, there is no difference in current consumption between transmission and reception during communication, so that no noise occurs.

It is apparent that the present invention is not limited to the above-described embodiment, but can be appropriately modified within the scope of the technical idea of the present invention. For example, as a method of flattening the difference in current consumption between transmission and reception, FIG. 1 illustrates a case where a correction current is supplied to a variable resistor grounded to the ground. By separately preparing the correction current, it is possible to store the correction current in this charge circuit during reception and discharge it from this charge circuit during transmission to flatten the difference in current consumption between transmission and reception. is there.

[0030]

As described above, according to the present invention, a variable resistor, a transistor, and a NAND
By adding a simple circuit such as a circuit, it is possible to eliminate the difference between the current consumption at the time of reception and the current consumption at the time of transmission, and to prevent the occurrence of noise, so that more ISDN lines are provided in the ISDN line package. There is an effect that can be accommodated.

According to the present invention, prior to communication with a subscriber, the line resistance of the line is calculated, and the resistance value of the variable resistor is set so as to flatten the difference in current consumption between transmission and reception, which differs for each subscriber line. Is determined, it is possible to prevent the generation of noise regardless of the line resistance.

[Brief description of the drawings]

FIG. 1 is a block diagram of a line termination device according to an embodiment of the present invention.

FIG. 2 AGC (Automatic Gain Co)
FIG. 9 is an explanatory diagram showing an operation of calculating a line resistance according to (n.

FIG. 3 is a diagram illustrating a relationship between an operation state of a line termination device and current consumption when a current correction circuit according to the present invention is added.

FIG. 4 is a diagram showing a relationship between an operation state of a conventional line termination device and current consumption.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 current correction circuit 101 power supply module section 102 transmission section 103 reception section 104 transmission and reception control section 105 N (normal) / R (reverse) control section 106, 107 switch 108 transformer 109 N / R switch 110 NAND circuit 111 transistor 112 variable resistor 113 Line 114 AGC switch

Claims (4)

[Claims] 1. A line terminating device connected to a subscriber via a line, repeats transmission and reception in a predetermined cycle in a time-division manner, and performs bidirectional communication with the subscriber. A line terminating apparatus comprising: a current correcting means for increasing the current consumption and increasing a difference between the current consumption at the time of transmission and performing on / off control of the current correcting means in response to the cycle. 2. The line termination device according to claim 1, wherein said current correction means is controlled to be in an on state during said reception, and is controlled to be in an off state during said transmission. 3. The line according to claim 1, wherein said current correction means includes a variable resistor for supplying a correction current at the time of reception, and a selection means for selecting a resistance value of said variable resistor. Terminating device. 4. The apparatus according to claim 1, further comprising means for detecting a line resistance of said line before communication with said subscriber, and selecting said resistance value according to a result of the detection. The line termination device according to any one of the above.