JPS5853233A - Matching system for balanced connection network - Google Patents

Abstract

PURPOSE:To always ensure the matching and to improve the speech quality, by providing plural balanced connection circuit networks and then selecting optimum one of these circuit networks. CONSTITUTION:A call current is supplied to a telephone from a DC power supply 34 via a feeding circuit 33 and a double wire line. The voltage which is generated between terminals 71 and 72 of the double wire line by the call current is detected by a voltage detector 37. The level of the detected voltage Vi is decided by comparators 38-1-38-n. Based on this result of decision, the optimum one is selected among balanced connection circuit networks 32-1-32-n by a selector 39. In such a wat, the voltage generated between the terminals 71 and 72 by a call current varies in response to the change of the resistance at the double wire that is due to the change of the type and length of the double wire line. Accordingly a balanced connection circuit network that is best matched with the resistance of the double wire side is selected. Thus the degree of unmatched attenuation can be kept large enough for a hybrid transforming circuit 31. Then the speech quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a balanced wire network matching method, particularly to a balanced wire network matching method in a communication device equipped with a 2-wire to 4-wire conversion circuit.

FIG. 1 shows an example of a communication device to which the present invention applies.
A subscriber circuit in the time division electronic exchange VC is shown, and FIG. 2 is a diagram showing an example of a conventional 2-wire to 4-wire conversion circuit of the subscriber circuit shown in FIG. 1.

In FIG. 1, a telephone 1 is connected to a subscriber circuit 3 via a two-way line 2, converted to a four-way system by a two-way to four-way switching circuit (not shown), and accommodated in a time division network 4. be done. As shown in FIG. 2, the two-way, one-fourth-way conversion circuit is realized by a hybrid transformer circuit 31 connected to a balanced wiring network 32. In FIG. 2, from the time division network 4 to the terminal 5 of the subscriber 1jjl path,
The digitally encoded reception signal transmitted to the terminals 71 and 72 is converted to an analog reception signal by the decoder 35, and then passed through the hybrid transformer circuit 31 to the terminals 71 and 72Vc.
It is transmitted to the 2nd Genshiki Genro 2 which is pasted. It is important to maintain the quality of calls that cannot be made via the time division network 4 by preventing the analog reception signal input from the decoder 35 to the hybrid transformer circuit 31 from being returned to the encoder 36Itllll11m as much as possible. It is necessary that the impedance of the balanced wire network 32 is sufficiently matched to the impedance (hereinafter referred to as 2-wire side impedance) K seen from the terminals 71 and 72 of the 2-line wire terminal 2 terminated at the telephone set 1. In a conventional subscriber circuit 3VC, the impedance of the XF balanced connection network 32 was fixedly determined to match the internal impedance of the telephone 1. However, since the two-wire side impedance differs from the internal impedance of the telephone 1 depending on the wire type and length of the two-wire line 2 used, matching with the balanced wiring network 32 is insufficient, and the hybrid transformer circuit The amount of mismatch attenuation of 31 also decreases, and the speech quality also deteriorates.

It is an object of the present invention to eliminate the drawbacks of the conventional balanced network matching method as described above, to match the impedance of the balanced network as much as possible even with the highly variable impedance of the two wires, and to maintain call rates. The problem lies in the actual state of the means to achieve this goal.

The purpose of this is to provide a means for determining the amount of DC power to be supplied to a two-wire line connected to a #2 wire type conversion circuit in a communication device equipped with a 2-wire to 4-wire conversion circuit, and a method for determining the amount of power. This is achieved by providing means for connecting a balanced wiring network corresponding to the impedance of the two-wire line to the two-wire to 4m conversion circuit.

An embodiment of the present invention will be described below with reference to FIG. Third
The figure is a diagram showing a balanced wire network matching system according to one embodiment 1+lJ of the present invention. Note that the same number indicates the same object throughout all the figures. In FIG. 3, a DC source 34 is applied between terminals 71 and 72 via a power supply circuit 33.
2+li! i! A telephone current is supplied to the telephone via Nishinro 2. As a result of the communication current supply, the normal line pressure generated between the terminals 71 and 72 is the sum of the internal resistance of the telephone 1 and the line resistance of the two-wire line 2 (hereinafter referred to as the two-wire side resistance),
Due to the internal resistance of the power supply circuit 33, the DC power supply 34 has a divided voltage value. Therefore, as the two-wire side resistance changes due to changes in the line type and width of the two-wire line 2, the line voltage also changes. If the resistance on the two-wire side approximately represents the impedance on the two-wire side, then the stratification of the line voltage is considered to approximately represent the change in the impedance on the two-wire side. Third
In the figure, a voltage detector 37 detects the line voltage and outputs a detected voltage V1. #The detection voltage Vi is connected in cascade and is supplied to each of 7'cn comparators 38-1 to 38-nK. The comparator 38-1 receives the input detection voltage Vi
Reference pressures VO and vI (Vo<V+
), and condition ■0≦vI≦V.

If this holds true, a selection signal C8 is sent out. Current standard city pressure V
o ”;: If the line resistance is O, then the detection voltage ■1 is the value indicated, and the twisted reference voltage V is the value indicated by the detection voltage Vi when the line resistance is 100 ohms, then the two-wire system is railroad track 2
The selection signal C5 is sent out when the line resistance of the line is 100 ohms or less. Also for the comparators 38-2 to 38-n,
Reference pressure V, to Vn corresponding to the line resistance range, respectively
(Vn is the detection voltage vIV when the line resistance is at the maximum allowable value)
By setting Cn (equivalent to C), the line resistance of the 2# type line 2 is reduced by the selection signals to Cn sent from any of the comparators 38-1 to 38-n in response to the input detection signal. The range is determined. These selection signals C1 to C
It is input to the n selector 39.

The selector 39 selects one of n types of balanced wiring networks -4=32-1 to 32-n provided to match the impedance on the two-wire side including the line resistance range determined by each selection signal C8 to Cn. , one corresponding to the input selection signals C7 to Cn is selected and connected to the hybrid transformer circuit 31.

As is clear from the above station connections, according to this embodiment, the balanced connection network connected to the Vibe II transformer circuit 31 is n
Connected to the current subscriber circuit 3 from the nm class balanced wiring networks 32-1 to 32-n, which are provided to match the impedance of the two-wire side including the line resistance range of the divided two-wire line 2. Since the one that best matches the existing two-wire side impedance is selected, the mismatch attenuation of the hybrid transformer circuit is maintained sufficiently large.

It should be noted that FIG. 3 is just one embodiment of the invention, and for example, the determination of 2,1ll111 resistance is not limited to the detection of the normal pressure between the lines; However, the effects of the present invention remain the same in either case. Furthermore, the present invention is not limited to the monophonic telephone 1 connected to the subscriber circuit 3 via the two-wire connection line 2, and the effects of the present invention remain the same in the case of other terminal devices. The 9z+ element of the present invention is not hidden in the subscriber circuit 3, and is applicable to general communication equipment that accommodates 2-wire circuits, including 2m-4 parallel circuits such as trunk circuits. However, the advantages of the present invention remain unchanged.

As described above, according to the present invention, in a communication device equipped with a 2-wire to 4-wire conversion circuit, even if T and the 2-wire impedance of the 2mg line to be accommodated become diverse, -ζ is also connected using a balanced wiring network that is matched. This makes it possible to maintain good call quality.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a subscriber circuit in a time-sharing multiplex switch which is the subject of the present invention, FIG. 2 is a diagram showing an example of a conventional 2-wire to 4-wire conversion circuit, and FIG. 3 is an example of an implementation of the present invention. FIG. 3 is a diagram illustrating a balanced wire network matching scheme according to an example; In the figure, 1 is a telephone, 2 is a two-wire line, 3 is a subscriber circuit, 4 is a time division network, 5.6.7.71 and 72 are terminals, 31 is a hybrid transformer circuit, 32 and 32-1 32-n to 32-n are balanced wiring networks, 33 is a power supply circuit, 34 is a DC power source, 35 is a beam encoder, 36 is an encoder, 3
7 is a voltage detector, 38-1 to 38-n are comparators, 39
selector, V i irJ, detection voltage, Vo to Vn
represents a reference voltage, and C3 to Cn represent selection signals. P1 Figure'yf72- Group 11 Figure 3

Claims (1)

[Claims] In a communication device equipped with a 2-wire to 4-wire conversion circuit,
A means for determining the amount of DC power to be supplied to the two-wire circuit connected to the Shinichi-4 Genshin conversion circuit; A balanced wire network matching method characterized by providing means for connecting to a wire-to-four wire conversion circuit.