Subscriber circuit

Abstract

The present invention comprises: a power supply device (51) that supplies a DC voltage between a first subscriber line (P1) and a second subscriber line (P2); and a letter coil (20) that is installed between the first subscriber line (P1) and the second subscriber line (P2) and the power supply device (51), and that blocks an AC signal. The power supply device (51) can change the DC voltage.

Description

Subscriber circuit

[0001] The present disclosure relates to a subscriber circuit that is installed closest to the telephone side of a switch and realizes the function of connecting to a telephone.

[0002] A subscriber circuit (SLIC; Subscriber Line Interface Circuit) that is installed closest to the telephone side of a switch and realizes the function of connecting to a telephone is composed of an integrated circuit using semiconductors.

[0003] LSI for analog subscriber circuit (Renesas Electronics), [searched on November 1, 2024], Internet <URL: https: / / www.renesas.com / ja / document / man / 705826?srsltid=AfmBOop_41UjW_R7MBeDn1cKTNse-IAHkQ9uHFfqAxcGfPGitP71Ee9H> LSI for analog subscriber circuit (Renesas Electronics), [searched on November 1, 2024], Internet <URL: https: / / www.renesas.com / ja / document / dst / 705681?srsltid=AfmBOoqsrA21g7aHIlNNqNT4Yq7G6obUHFkgDKpwMXPDdn0Vlhg3T28S>

[0004] However, the structure of the subscriber circuit corresponding to a high voltage is greatly different from other integrated circuits, and the production difficulty is high. Furthermore, due to the increasing demand for semiconductors recently, it may not be possible to immediately obtain an integrated circuit for the subscriber circuit to meet the production requirements of the subscriber circuit.

[0005] Non-Patent Documents 1 and 2 disclose subscriber circuits using passive elements such as coils and capacitors. The subscriber circuits disclosed in Non-Patent Documents 1 and 2 do not require semiconductors, and furthermore, the above passive elements are easily available, so they can immediately respond to production requirements. However, although the subscriber circuits disclosed in Non-Patent Documents 1 and 2 have a power supply for supplying a DC voltage to the subscriber line, since the output voltage is constant, the loop current flowing through the subscriber line cannot be adjusted, and there is a problem of wasting power due to excessive current supply.

[0006] This disclosure has been made in view of the above circumstances, and its purpose is to provide a subscriber circuit that can suppress the use of integrated circuits and prevent excessive current from flowing through the subscriber line.

[0007] A subscriber circuit according to one aspect of the present disclosure comprises a power supply device that supplies a DC voltage between a first subscriber line and a second subscriber line, and a passive element circuit installed between the first subscriber line and the second subscriber line and the power supply device for blocking AC signals, wherein the power supply device is capable of changing the DC voltage.

[0008] This disclosure makes it possible to reduce the use of integrated circuits and prevent excessive current from flowing through subscriber lines.

[0009] Figure 1 is a circuit diagram showing the configuration of a subscriber circuit according to the first embodiment. Figure 2 is a circuit diagram showing the configuration of a subscriber circuit according to a comparative example. Figure 3 is a circuit diagram showing the configuration of a subscriber circuit according to the second embodiment. Figure 4 is a circuit diagram showing the configuration of a subscriber circuit according to the third embodiment. Figure 5 is a circuit diagram showing the configuration of a subscriber circuit according to the fourth embodiment. Figure 6 is a circuit diagram showing the configuration of a subscriber circuit according to the fifth embodiment. Figure 7 is a circuit diagram showing the configuration of a subscriber circuit according to the sixth embodiment. Figure 8 is a circuit diagram showing the configuration of a subscriber circuit according to the seventh embodiment.

[0010] [Description of the First Embodiment] Hereinafter, embodiments will be described with reference to the drawings. Figure 1 is a circuit diagram of the subscriber circuit 101 according to the first embodiment. As shown in Figure 1, the subscriber circuit 101 comprises a hybrid transformer 10, a letter coil 20 (passive element circuit), a balanced network 30, and a power supply 51.

[0011] The hybrid transformer 10 is equipped with a 4-wire coil L11 and 2-wire coils L12 and L13, and performs 2-wire / 4-wire conversion. The hybrid transformer 10 isolates the circuits on the coils L12 and L13 from the circuits on the coil L11 side.

[0012] One end of coil L11 is connected to the 4-wire output terminal Tx via resistor Ra. The other end of coil L11 is connected to the 4-wire input terminal Rx via resistor Rb. The center tap TP of coil L11 is connected to the balanced network 30. One end of the balanced network 30 is connected to the midpoint 11 between the output terminal Tx and the input terminal Rx, and is also grounded. The balanced network 30 maintains voltage balance at the center tap TP of coil L11.

[0013] Coils L12 and L13 are connected via capacitor C1. Capacitor C1 removes the DC component of the current flowing through coils L12 and L13. That is, one end of coils L12 and L13 is connected to capacitor C1. The other end of coil L12 is connected to connection terminal 12 (labeled "Tip" in the diagram) for subscriber line connection via resistor R12. The other end of coil L13 is connected to connection terminal 13 (labeled "Ring" in the diagram) for subscriber line connection via resistor R13.

[0014] Connection terminal 12 is connected to the first subscriber line P1, and connection terminal 13 is connected to the second subscriber line P2. The first subscriber line P1 and the second subscriber line P2 are connected to a telephone (not shown). The loop resistance of the first subscriber line P1 and the second subscriber line P2 is denoted as RL, and the current flowing through the loop resistance RL is denoted as the loop current IL.

[0015] The letter coil 20 is installed between the two connection terminals 12 and 13 and the power supply unit 51. The letter coil 20 includes a series connection circuit of coil L1 and resistor R1, and a series connection circuit of coil L2 and resistor R2. The letter coil 20 is installed between the first subscriber line P1 and the second subscriber line P2 and the power supply unit 51 to interrupt AC signals. The letter coil 20 is composed of passive elements such as coils and resistors and is an example of a passive element circuit that interrupts AC signals.

[0016] One end of coil L1 is connected to connection terminal 12, and the other end is connected to terminal q1 of the power supply 51 via resistor R1. One end of coil L2 is connected to connection terminal 13, and the other end is connected to terminal q2 of the power supply 51 via resistor R2. Terminal q1 is grounded.

[0017] The power supply unit 51 supplies a DC voltage between the first subscriber line P1 and the second subscriber line P2. In other words, the power supply unit 51 is a power supply for central office power supply. The output voltage of the power supply unit 51 is adjustable. The power supply unit 51 is equipped with three switches S1 to S3 (switch section) and three voltage sources E1 to E3. Switch S1 and voltage source E1 are connected in series, switch S2 and voltage source E2 are connected in series, and switch S3 and voltage source E3 are connected in series. Each series connection circuit is connected in parallel with each other, and both ends are connected to terminals q1 and q2. The three switches S1 to S3 constitute the switch section.

[0018] The output voltages of each voltage source E1 to E3 are set to different values. Each switch S1 to S3 is connected to, for example, a switching device (not shown), and is controlled to be on or off so that one switch is selectively turned on. The output voltage of one of the voltage sources E1 to E3 is supplied between terminal q1 and terminal q2. In other words, the power supply unit 51 comprises a plurality of voltage sources E1 to E3 with different output voltages, and a switching unit (switches S1 to S3) that selects one of the plurality of voltage sources E1 to E3 and supplies it between the first subscriber line P1 and the second subscriber line P2.

[0019] By installing the letter coil 20 between the power supply unit 51 and each connection terminal 12, 13, the impedance between each connection terminal 12, 13 and the power supply unit 51 can be made AC high, preventing the power supply unit 51 from affecting the audio signal.

[0020] The audio signal input from the 4-wire input terminal Rx is transmitted to the 2-wire side by the hybrid transformer 10, and then transmitted to the telephone via the first subscriber line P1 and the second subscriber line P2 from the connection terminals 12 and 13. The audio signal input from the telephone is transmitted to the 4-wire side by the hybrid transformer 10 via the first subscriber line P1 and the second subscriber line P2, and then transmitted to the output terminal Tx on the 4-wire side via the connection terminals 12 and 13.

[0021] In such a subscriber circuit 101, the DC voltage supplied to the two subscriber lines P1 and P2 can be changed by switching the on and off of each switch S1 to S3. Figure 2 is a circuit diagram showing a subscriber circuit 100 according to a comparative example. In the comparative example shown in Figure 2, a voltage source E that outputs a DC voltage is provided as a power supply for central office power supply. The configuration other than the voltage source E is the same as in Figure 1, so the same reference numerals are used and the explanation of the configuration is omitted. In the comparative example shown in Figure 2, the power supply voltage for central office power supply is constant. Therefore, even if the loop current IL fluctuates due to a change in the loop resistance RL, the DC voltage supplied to the two subscriber lines cannot be changed. Consequently, the loop current IL cannot be adjusted to a desired current value.

[0022] In the subscriber circuit 101 according to the first embodiment, voltage sources E1 to E3 are provided as power sources for central office power supply. By switching switches S1 to S3 on and off, it is possible to select a voltage source that outputs a desired voltage from among the voltage sources E1 to E3 and supply power to the first subscriber line P1 and the second subscriber line P2.

[0023] As described above, the subscriber circuit according to this embodiment includes a power supply device 51 that supplies a DC voltage between the first subscriber line P1 and the second subscriber line P2, and a passive element circuit (letter coil 20) installed between the first subscriber line P1 and the second subscriber line P2 and the power supply device 51 to block AC signals, and the power supply device 51 is capable of changing the DC voltage.

[0024] In this embodiment, the subscriber circuit 101 can be configured using readily available passive elements such as coils and capacitors to form the letter coil 20. Specifically, the coils L1 and L2 provided in the letter coil 20 can be made by winding electric wire around a magnetic core, and are therefore readily available. Similarly, the hybrid transformer 10 can also be configured using passive elements such as coils and capacitors. In other words, since integrated circuits equipped with semiconductors are not used or their usage is reduced, it becomes possible to respond immediately to production demands.

[0025] The subscriber circuit 101 according to this embodiment is equipped with three voltage sources E1 to E3 with different output voltages as power supplies for central office power supply, and any of the voltage sources can be selected to supply voltage to each subscriber line P1 and P2. Therefore, the loop current IL can be adjusted to a desired current value, and problems such as wasting power due to excessive current supply can be avoided. In this embodiment, the subscriber circuit 101 is configured by combining readily available passive elements with a power supply device 51 that has a variable output voltage, thereby increasing the degree of control flexibility.

[0026] In this embodiment, an example using three voltage sources E1 to E3 and three switches S1 to S3 has been described, but a configuration using two or more voltage sources and switches is also possible.

[0027] [Description of the Second Embodiment] Next, a second embodiment will be described. Figure 3 is a circuit diagram showing the configuration of the subscriber circuit 102 according to the second embodiment. The subscriber circuit 102 according to the second embodiment differs from the subscriber circuit 101 shown in Figure 1 above in that the power supply unit 52 includes an ammeter 41 and a control unit 40 in addition to switches S1 to S3 and voltage sources E1 to E3. The ammeter 41 is installed between the connection terminal 13 and the coil L2. That is, the power supply unit 52 includes an ammeter 41 that measures the current flowing through the letter coil 20 and a control unit 40 that sets the DC voltage output by the power supply unit 52 based on the current measured by the ammeter 41. The other components are the same as in Figure 1, so the same reference numerals are used and their description is omitted.

[0028] The control unit 40 controls the system to turn on one of the switches S1 to S3 based on the current measured by the ammeter 41. The control unit 40 can be configured as an integrated computer consisting of, for example, a central processing unit (CPU) and storage devices such as RAM, ROM, and hard disk.

[0029] In the subscriber circuit 102 according to the second embodiment, the current flowing through the letter coil 20 is measured by an ammeter 41. Based on the current measured by the ammeter 41, the control unit 40 selects and turns on one of switches S1 to S3. As a result, a DC voltage corresponding to the current flowing through the letter coil 20 can be supplied between each subscriber line P1 and P2. Therefore, the loop current IL can be adjusted to a desired current value, and problems such as wasting power due to excessive current supply can be avoided. Furthermore, since integrated circuits using semiconductors are not used or their usage can be reduced, the electrical components constituting the subscriber circuit 102 can be easily obtained.

[0030] Note that the installation location of the ammeter 41 is not limited to the space between the connection terminal 13 and the coil L2 shown in Figure 3; it may be installed in any other location where the current flowing through the letter coil 20 can be measured.

[0031] [Description of the Third Embodiment] Next, a third embodiment will be described. Figure 4 is a circuit diagram showing the configuration of the subscriber circuit 103 according to the third embodiment. The subscriber circuit 103 according to the third embodiment differs from the subscriber circuit 101 shown in Figure 1 above in that the power supply unit 53 includes a voltmeter 42 and a control unit 40 in addition to switches S1 to S3 and voltage sources E1 to E3. The voltmeter 42 is installed between connection terminals 12 and 13. That is, the power supply unit 53 includes a voltmeter 42 that measures the voltage between the first subscriber line P1 and the second subscriber line P2, and a control unit 40 that sets the DC voltage output by the power supply unit 53 based on the voltage measured by the voltmeter 42. The other configurations are the same as in Figure 1, so the same reference numerals are used and their description is omitted.

[0032] The control unit 40 controls the system to turn on one of the switches S1 to S3 based on the voltage value measured by the voltmeter 42.

[0033] In the subscriber circuit 103 according to the third embodiment, a voltmeter 42 measures the voltage supplied between two connection terminals 12 and 13. Based on the voltage value measured by the voltmeter 42, the control unit 40 selects and turns on one of switches S1 to S3. As a result, a DC voltage corresponding to the voltage value between the two connection terminals 12 and 13 can be supplied between each subscriber line P1 and P2. Therefore, the loop current IL can be adjusted to a desired current value, and problems such as wasting power due to excessive current supply can be avoided. Furthermore, since integrated circuits using semiconductors are not used or their usage is reduced, the electrical components constituting the subscriber circuit 103 can be easily obtained.

[0034] [Description of the Fourth Embodiment] Next, the fourth embodiment will be described. Figure 5 is a circuit diagram showing the configuration of the subscriber circuit 104 according to the fourth embodiment. The subscriber circuit 104 according to the fourth embodiment differs from the subscriber circuit 101 shown in Figure 1 above in that the power supply unit 54 is equipped with a variable power supply EV instead of the three voltage sources E1 to E3. Specifically, the variable power supply EV is installed between resistors R1 and R2. The other configurations are the same as in Figure 1, so the same reference numerals are used and their description is omitted.

[0035] The variable power supply EV is connected to, for example, a switching device (not shown), and the output DC voltage can be continuously changed by controlling the switching device. That is, the DC voltage supplied between terminals q1 and q2 can be set to any desired voltage.

[0036] In the subscriber circuit 104 according to the fourth embodiment, the voltage supplied to each subscriber line P1 and P2 can be set to a desired voltage by manipulating the output voltage of the variable power supply EV. Therefore, the loop current IL can be adjusted to a desired current value, and problems such as wasting power due to excessive current supply can be avoided. Furthermore, since integrated circuits using semiconductors are not used or their usage is reduced, the electrical components constituting the subscriber circuit 104 can be easily obtained.

[0037] [Description of the Fifth Embodiment] Next, the fifth embodiment will be described. Figure 6 is a circuit diagram showing the configuration of the subscriber circuit 105 according to the fifth embodiment. The subscriber circuit 105 according to the fifth embodiment differs from the subscriber circuit 104 according to the fourth embodiment shown in Figure 5 above in that the power supply device 55 includes an ammeter 41 and a control unit 40 in addition to the variable power supply EV. The ammeter 41 is installed between the connection terminal 13 and the coil L2. The other components are the same as in Figure 1, so the same reference numerals are used and their description is omitted.

[0038] The control unit 40 controls the output voltage of the variable power supply EV to a desired voltage based on the current measured by the ammeter 41.

[0039] In the subscriber circuit 105 according to the fifth embodiment, the current flowing through the letter coil 20 is measured by an ammeter 41. The control unit 40 sets the output of the variable power supply EV based on the current measured by the ammeter 41. Therefore, the loop current IL can be adjusted from the current value before setting the output of the variable power supply EV to a desired current value. Accordingly, similar to the fourth embodiment described above, the loop current IL can be adjusted to a desired current value, and problems such as wasting power due to excessive current supply can be avoided. Furthermore, since integrated circuits using semiconductors are not used or their usage is reduced, the electrical components constituting the subscriber circuit 105 can be easily obtained.

[0040] Note that the installation location of the ammeter 41 is not limited to the space between the connection terminal 13 and the coil L2 shown in Figure 6; it may be installed in any other location where the current flowing through the letter coil 20 can be measured.

[0041] [Description of the Sixth Embodiment] Next, the sixth embodiment will be described. Figure 7 is a circuit diagram showing the configuration of the subscriber circuit 106 according to the sixth embodiment. The subscriber circuit 106 according to the sixth embodiment differs from the subscriber circuit 105 according to the fourth embodiment shown in Figure 5 above in that the power supply device 56 includes a voltmeter 42 and a control unit 40 in addition to the variable power supply EV. The voltmeter 42 is installed between connection terminals 12 and 13. The other components are the same as in Figure 5, so the same reference numerals are used and their description is omitted.

[0042] The control unit 40 performs control to set the output voltage of the variable power supply EV to a desired voltage based on the voltage value measured by the voltmeter 42.

[0043] The subscriber circuit 106 according to the sixth embodiment measures the voltage between the two connection terminals 12 and 13 by the voltmeter 42. The control unit 40 sets the output voltage of the variable power supply EV based on the voltage value measured by the voltmeter 42. Therefore, the voltage value between the two connection terminals 12 and 13 can be adjusted from the voltage value before setting the variable power supply EV to the desired voltage value. As a result, the loop current IL can be adjusted to the desired current value. Therefore, similar to the fourth embodiment described above, the loop current IL can be adjusted to the desired current value, and problems such as power waste due to excessive current supply can be avoided. In addition, since an integrated circuit using a semiconductor is not used or the usage amount is reduced, the electrical components constituting the subscriber circuit 106 can be easily obtained.

[0044] [Description of the Seventh Embodiment] Next, the seventh embodiment will be described. FIG. 8 is a circuit diagram showing the configuration of the subscriber circuit 107 according to the seventh embodiment. The subscriber circuit 107 according to the seventh embodiment is different from the subscriber circuit 101 shown in FIG. 1 described above in that the power supply device 57 includes a current source EI. Specifically, a current source EI capable of changing the current is installed between the resistors R1 and R2. Since the other configurations are the same as those in FIG. 1, the same reference numerals are given and the description is omitted.

[0045] The current source EI is connected to, for example, a switching device (not shown), and the current flowing through the letter coil 20 can be continuously changed by the control of the switching device. That is, the direct current flowing between the terminal q1 and the terminal q2 can be set to an arbitrary current.

[0046] In the subscriber circuit 107 according to the seventh embodiment, the current supplied to each subscriber line P1 and P2 can be set to a desired current by operating the current source EI. Therefore, the loop current IL can be adjusted to a desired current value, and problems such as wasting power due to excessive current supply can be avoided. Furthermore, since integrated circuits using semiconductors are not used or are used in small quantities, the electrical components constituting the subscriber circuit 107 can be easily obtained.

[0047] This disclosure is not limited to the embodiments described above, and numerous modifications are possible within the scope of its essence.

[0048] 10 Hybrid transformer 12, 13 Connection terminals 20 Letter coil 30 Balanced network 40 Control unit 41 Ammeter 42 Voltmeter 51-57 Power supply unit 101-107 Subscriber circuit E1-E3 Voltage source EI Current source EV Variable power supply IL Loop current P1 First subscriber line P2 Second subscriber line S1-S3 Switch (switch unit)

Claims

1. A subscriber circuit comprising: a power supply device that supplies a DC voltage between a first subscriber line and a second subscriber line; and a passive element circuit installed between the first subscriber line and the second subscriber line and the power supply device for blocking AC signals, wherein the power supply device is capable of changing the DC voltage.

2. The subscriber circuit according to claim 1, comprising: a power supply unit comprising: a plurality of voltage sources with different output voltages; and a switch unit that selects one of the plurality of voltage sources and supplies voltage between the first subscriber line and the second subscriber line.

3. The subscriber circuit according to claim 1, further comprising: an ammeter for measuring the current flowing through the passive element circuit; and a control unit for setting the DC voltage output by the power supply based on the current measured by the ammeter.

4. The subscriber circuit according to claim 1, comprising: a power supply unit comprising: a voltmeter for measuring the voltage between the first subscriber line and the second subscriber line; and a control unit for setting the DC voltage output by the power supply unit based on the voltage measured by the voltmeter.

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