JP3023846U - Out-of-band signal separation and superposition circuit - Google Patents

Abstract

(57) Abstract: It is possible to prevent quality deterioration due to reflection, echo, distortion, etc. when an out-of-voice signal is transmitted separately from an audio frequency signal. An out-of-band signal separation circuit or a superposition circuit for separating out-of-band signals is provided with a bridging T-type filter whose impedance between terminals connected to a subscriber line approximates to the characteristic impedance of the subscriber line. .

Description

[Detailed description of the device]

[0001]

[Technical field to which the device belongs]

 The present invention is used in equipment for analog telephones. The present invention relates to an improvement in a technique for passing an out-of-band signal other than the voice frequency signal through the analog telephone line in addition to the voice band frequency. This out-of-band signal is used for monitoring, telemetry, remote control, etc. INDUSTRIAL APPLICABILITY The present invention can be used in a technique for superimposing a supervisory signal on an analog telephone line. The present invention can be used for telemetering using a telephone subscriber line. The present invention is intended to prevent deterioration of quality due to reflection, distortion, or echo in the signal of the original voice band frequency when an out-of-band signal is added. Of technology.

[0002]

[Prior art]

 Fig. 1 shows the configuration of a line monitoring system that transmits a monitoring signal of an out-of-voice signal to a telephone subscriber line to monitor terminals and the like. In this line monitoring system, for example, a monitoring signal from a monitoring device provided in a terminal and a detection signal (monitoring signal) from a telemetering device are transmitted to a center device via a telephone subscriber line.

In the line monitoring system of FIG. 1, a monitoring signal transmitting device 1 provided in terminal equipment is connected to a line monitoring device 2 provided in a station via a subscriber line 10. The line monitoring device 2 is connected to the exchange 9. The supervisory signal sending device 1 is provided between the analog telephone terminal 8 and a supervisory signal generating circuit 4 for producing a supervisory signal, and a supervisory signal superposing circuit 3 for superposing this supervisory signal on a voice band signal. ing. Further, the line monitoring device 2 includes a supervisory signal separating circuit 5 for separating supervisory signals, a supervisory signal measuring circuit 6 for measuring the level of the supervisory signal, and a supervisory alarm based on the measurement result of the supervisory signal measuring circuit 6. And a monitoring / alarm circuit 7 for outputting the above.

As shown in FIG. 2, the supervisory signal superimposing circuit 3 of the supervisory signal transmitting apparatus 1 and the supervisory signal separating circuit 5 of the line supervisory apparatus 2 include a low pass filter (LPF) 11 and a high pass filter ( HPF) 12 is combined, and a low-pass filter 11 is inserted between the analog telephone terminal 8 or the exchange 9 and the subscriber line 10, and the high-pass filter 12 of the subscriber line side is inserted. One is connected and the other is connected to the supervisory signal generating circuit 4 or the supervisory signal measuring circuit 6. Since the low-pass filter 11 and the high-pass filter 12 cannot receive power supply from the line or the outside, they do not use active elements as circuit components, and are composed of passive element coils and capacitors. .

FIG. 3A shows the attenuation characteristics of the low pass filter 11 and the high pass filter 12. The low-pass filter 11 passes the call band signal 13 but blocks the monitor signal 14 outside the band. The high-pass filter 12 allows the supervisory signal 14 to pass but blocks the speech band signal 13.

FIG. 3B shows the input impedance characteristics of the low-pass filter 11 and the high-pass filter 12. The low-pass filter 11 has a terminal impedance R ₀ in the speech signal band 15 and has a high impedance in the supervisory signal frequency 16. The high-pass filter 12 has a terminating impedance R ₀ at the supervisory signal frequency 16 and has a high impedance at the call signal band 15.

The operation of the line monitoring system shown in FIG. 1 will be described.

The supervisory signal 14 output from the supervisory signal generation circuit 4 passes through the high-pass filter 12 and is sent to the subscriber line 10. However, the analog telephone terminal 8 side uses the low-pass filter 11 to send it. Further, since the low-pass filter 11 has a high impedance at the supervisory signal frequency 16, the analog telephone terminal 8 is not affected by the supervisory signal. Similarly, the call band signal 13 from the analog telephone terminal 8 is sent to the subscriber line 10 without being affected by the supervisory signal generating circuit 4.

The supervisory signal 14 transmitted through the subscriber line 10 and reaching the inside of the station passes through the high pass filter 12 and is output to the supervisory signal measuring circuit 6, and the speech band signal 13 is a low pass filter. The signal passes through 11 and is output to the exchange 9. The supervisory signal 14 is blocked by the low pass filter 11 and is not affected by the exchange 9 at the supervisory signal frequency 16 because the low pass filter 11 has a high impedance. Similarly, the call band signal 13 is separated by the high pass filter 12 without being affected by the supervisory signal measuring circuit 6.

[0010]

[Problems to be solved by the device]

 The branching circuit composed of the low-pass filter 11 and the high-pass filter 12 is generally designed with a terminating impedance as a pure resistance. This is because the input / output impedance handled is a pure resistance and a fixed value of 600 Ω is used in the voice transmission system device, and the signal level is regulated by this.

On the other hand, in the subscriber line, the self-inductance and leakage conductance as line constants are small and negligible in the voice band range, so the line is a distributed constant circuit consisting of conductor resistance and line capacitance. Can be approximated. Conductor resistance is R, capacitance is C, and line characteristic impedance is Z₀Then, Z₀= √ (R / ωC), the characteristic impedance Z₀The magnitude of γ decreases with increasing frequency. Also, characteristic impedance Z₀Is not a pure resistance but a complex number of R and C. As an example, FIG. 4 shows the characteristic impedance Z of the balanced pair cable.₀  Example (cable with diameter 0.4 mm and 0.65 mm) is shown, but its impedance does not match the 600 Ω which is the input / output impedance of the device because its impedance changes depending on the frequency.

In the branching circuit to which the subscriber line is connected, the impedance seen from the analog telephone terminal 8 side or the exchange 9 side of the low-pass filter 11 as seen from the line side is not matched as described above. However, the line impedance characteristic 17 as it is cannot be seen, and as the frequency becomes higher, the difference becomes larger and undulation appears. FIG. 5 shows an example 18 of changes in impedance when the branching circuit is inserted when the fourth-order low-pass filter 11 is adopted. When the low-pass filter 11 is not matched, this waviness occurs because the combination of the elements of the coil and the capacitor that form the filter cause parallel resonance and series resonance.

Further, as shown in FIG. 6, a hybrid circuit for converting a two-wire line used on the analog telephone terminal 8 side or the exchange 9 side into a four-wire line composed of a transmission line 19 and a reception line 20. In 21, the balanced connection network B N22 is matched to the line impedance characteristic 17 so that the amount of attenuation of the signal from the transmission line 19 to the reception line 20, that is, the echo loss 23 can be made large when the line is connected. Is set to.

From this, by inserting the demultiplexing circuit into the subscriber line, the line impedance characteristic 17 seen from the device changes, so that the echo loss 23 of the hybrid circuit 21 decreases and the analog telephone terminal 8 , Leakage from the transmitter to the receiver, that is, the side tone becomes loud and the call becomes difficult to make, or the exchange 9 causes an echo because part of the signal sent to the other party is returned to the sender. There was a quality problem.

Further, when trying to improve the low-pass filter 11 so as to match the line impedance characteristic 17, the line impedance is expressed by a complex number of R and C. Therefore, the low-pass filter 11 itself is a coil and a capacitor. Since it cannot be configured with a reactance circuit consisting of, the circuit configuration includes a resistor in the circuit, resulting in a large insertion loss and further complicating the circuit and increasing the cost.

The present invention solves the problems of these conventional examples. Even when inserted into the subscriber line, the impedance seen from the line side is less changed than the impedance characteristic of the line. The purpose is to realize a separation circuit. In addition, the purpose of this proposal is to prevent the deterioration of the communication quality due to reflection, distortion, and echo when transmitting an out-of-voice signal using a subscriber line.

[0017]

[Means for Solving the Problems]

 A first aspect of the present invention relates to an out-of-band signal separation circuit, which is connected to a subscriber line in an out-of-band signal separation circuit for separating out-of-band signals transmitted outside the voice band of an analog telephone subscriber line. It is characterized in that it has a bridging T-type filter whose impedance between terminals is similar to the characteristic impedance of the subscriber line.

A second aspect of the present invention relates to an out-of-band signal superimposing circuit, which superimposes an out-of-band signal superimposing circuit for transmitting an out-of-band signal transmitted outside the voice band of the analog telephone subscriber line, to the subscriber. It is characterized in that it has a bridging T-type filter whose impedance between terminals connected to the line approximates the characteristic impedance of the subscriber line.

By using such an out-of-band signal separation circuit and an out-of-band signal superposition circuit, when an out-of-band signal is transmitted, reflection, distortion, echo, etc. occur in the original voice band signal, resulting in speech quality. It is possible to prevent the data transmission quality from deteriorating.

The impedance between the terminals of the bridge T-type filter is preferably about 600Ω. Further, it is preferable that the bridge T-type filter is a band-stop filter including an out-of-band signal in its stop frequency band.

Further, as a circuit for passing the out-of-band signal to the subscriber line side terminal of the bridge T-type filter for blocking the out-of-band signal, an impedance higher than that of a normal high-pass filter or characteristic impedance is provided. It is possible to have a device configuration in which a circuit for performing high DC cutoff, for example, a transformer or a resistor-capacitor series circuit is connected.

Further, the separation circuit or the superposition circuit is provided with a high-pass filter and a low-pass filter, and one of the high-pass filter and the low-pass filter is a bridging T-type filter. You can

In addition, the separation circuit or the superposition circuit is provided with a high-pass filter and a low-pass filter, and the high-pass filter and the low-pass filter are both bridging T-type filters. be able to.

Further, the bridge T-type filter may be a balanced pair type or an unbalanced type.

A constant impedance bridge T-type band stop filter circuit is inserted between the analog telephone terminal and the subscriber line or between the exchange and the subscriber line. This constant-impedance bridge T-type band elimination filter circuit has a large attenuation at the frequency of the monitoring signal, which is an out-of-speech signal, and becomes an actual impedance. The monitoring signal can be superimposed or separated regardless of the state. Since the deviation from the line impedance when the circuit is inserted in the subscriber line can be made smaller than before, side effects and echoes can reduce the effect on communication quality. Moreover, since the number of elements can be reduced as compared with the conventional demultiplexing circuit configuration, the circuit can be simplified and the cost can be reduced.

[0026]

[Embodiment of device]

 Embodiments of the present invention will be described below with reference to the drawings. First Embodiment FIG. 7 shows the circuit configuration of the supervisory signal superimposing circuit 3 used in the supervisory signal transmitting device 1 in FIG. This supervisory signal superimposing circuit uses a resistor R, an inductance L, and a constant resistance circuit network bridge bridge T-type band stop filter (BEF) 24 using a capacitor C and a supervisory signal 14 from a supervisory signal generating circuit 4 to a subscriber. It consists of a circuit for coupling to a wire. In this example, the telephone line is a balanced transmission line and is therefore a balanced circuit.

In this embodiment, in the supervisory signal superimposing circuit 3 for superimposing a supervisory signal which is an out-of-band signal of the analog telephone subscriber line, the impedance between terminals is approximate to the characteristic impedance of the subscriber line 10. It is characterized in that it is provided with a bridging T-shaped band stop filter 24.

[0028] The band-stop filter 24, a capacitor C ₁ and inductance L ₁ inductance connection point of the parallel circuit and the resistor R _0/2 connected in parallel circuit with two resistive series circuit of R _0/2 and L _This is a circuit configuration in which a series circuit of ₂ and a capacitor C ₂ is connected. The output of the monitor signal generating circuit 4 is connected to the line by a resistor R _1/2 and the series circuit of the capacitor C _3/2.

The characteristic of the band elimination filter 24 is shown in FIG. 8. The band elimination filter 24 has the attenuation characteristic 25 shown in FIG. 8 and blocks passage of the supervisory signal frequency f _c .

The band rejection filter 24, that does not leak monitoring signal 14 to the terminal side, given the impedance of the terminal equipment in the monitoring signal frequency 16 (f _c) is a change in level monitor signal is also me any state der It is necessary not to.

Items to be considered in designing the band elimination filter 24 will be described. The band-stop filter 24 has the attenuation characteristic 25 shown in FIG. 8, but provides the attenuation amount A and the bandwidth b as design parameters. The difference between the inaudible level of the supervisory signal frequency f _c in the analog telephone terminal 8 and the supervisory signal level to be transmitted is the attenuation amount A required for the band elimination filter 24. Further, in consideration of the stability of the circuit element, the bandwidth b that can secure the attenuation amount A is required. Here, if the bandwidth b is set too large, the change in the line impedance, which is the object of the present invention, cannot be suppressed to a small extent, and there is a problem that the loss in the speech band becomes large. It should be kept to a minimum. Since the impedance of the band elimination filter 24 depends on the impedance connected in the pass band, it does not need to be taken into consideration in the design, and the impedance at the stop frequency may be set. And Although the circuit of this embodiment is a balanced circuit network, each element value is obtained by the following equation as an unbalanced circuit for simplification in design as shown in FIG.

[0032]

[Equation 1] The circuit that combines the signals from the supervisory signal generation circuit 4 must not affect the call signal. If the impedance is 10 times or more the impedance of the device on the terminal side, there is no problem in practical use, so R ₁ is selected as the value. Since no direct current should be applied, the capacitor C ₃ separates. When the line side is terminated by R ₀ , the level from the supervisory signal generating circuit 4 is attenuated by the partial pressure of R ₀ / (2R ₁ + R ₀ ), so the output level of the supervisory signal generating circuit 4 is that much. Decide in consideration.

In the supervisory signal superimposing circuit 3 thus configured, the impedance when the line is connected has the impedance characteristic 26 when the band elimination filter 24 of FIG. 10 is inserted. Within the speech band, the deviation from the line impedance characteristic 17 is smaller than that of the conventional demultiplexing circuit. If the band width of the band elimination filter 24 is narrowed, the impedance characteristic can be brought closer to the line impedance characteristic 17, but this is a problem in terms of element stability and cost. In the circuit of this embodiment, each section constituting the circuit resonates only with the supervisory signal as compared with the conventional circuit, and therefore, when a load that does not match is connected, it is close to the pass band like the conventional branching circuit. By the way, the impedance does not fluctuate due to some resonances of different frequencies, and because of the constant resistance network, it is suppressed to the impedance of R ₀ at resonance. Naturally, it is desirable that the line impedance characteristic 17 is brought close to other than the call band. However, by decreasing R ₀ , the high frequency band can be brought closer, but since the deviation in the call band becomes large, it is better to bring the call band closer in order to improve the sidetone level, and R ₀ is made too small. should not do.

Second Embodiment FIG. 11 shows an embodiment of the supervisory signal separation circuit 5 used in the line supervisory apparatus 2 of FIG.

The configuration of the band elimination filter 24 here is exactly the same as that of FIG. The transformer T ₁ and the capacitor C ₄ are for connecting the supervisory signal 14 from the line to the supervisory signal measuring circuit 6 with a high impedance without affecting the signal in the speech band, and the transformer T ₁ is R _0. Is a transformer having an impedance of 10 times or more, and C ₄ is for DC blocking. At the supervisory signal frequency 16 by the band stop filter 24, the impedance seen from the line side is a constant resistance R ₀ regardless of the impedance state of the exchange 9 side, and the supervisory signal 14 is not affected by the supervisory signal measuring circuit 6. Supplied.

In the circuit of the present embodiment, unlike the conventional demultiplexing circuit, the call band signal 13 is simultaneously input to the monitor signal measuring circuit 6, so the call band signal 13 is removed and only the monitor signal 14 is selected. A bandpass filter (BPF) 27 is required. In the conventional branching circuit, the call band signal 13 is blocked by the high-pass filter 12, and the filter for blocking the call signal is not necessary for the supervisory signal measuring circuit 6, but the high-pass filter of this circuit is used. Since 27 can be constituted by active elements, there is an advantage that the cost is not higher than the conventional one.

Although the above-described first and second embodiments are examples in which the balanced band stop filter is used as the band stop filter, when the subscriber line is an unbalanced line such as a coaxial cable. For this, the unbalanced band elimination filter shown in FIG. 9 may be used.

[0038]

[Effect of device]

 As described above, by using the band elimination filter of the constant resistance network as the supervisory signal superimposing circuit or the supervisory signal separating circuit, it is possible to reduce the difference between the impedance characteristics seen from the device side and the impedance characteristics of the line. Therefore, it is possible to increase the echo loss of the hybrid circuit of the analog telephone terminal and the exchange, and reduce the deterioration of the call quality due to the increase of sidetone and the generation of echo. Further, the circuit can be simplified as compared with the conventional one, so that the cost can be reduced.

Also, when applied to a telemetering method used for remote measurement of equipment on the terminal side from a station side using a subscriber line, problems such as reflection, echo, and distortion occur in a voice band signal, and data transmission. It is possible to suppress deterioration of quality.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a line monitoring system.

FIG. 2 is a diagram showing a configuration of a conventional supervisory signal superimposing circuit and separating circuit.

FIG. 3 is a diagram showing characteristics of a demultiplexing circuit including a low-pass filter and a high-pass filter.

FIG. 4 is a diagram showing an example of a characteristic impedance of a balanced pair cable.

FIG. 5 is a diagram showing a change in impedance when a branching circuit is inserted.

FIG. 6 is a diagram showing an example of a hybrid circuit.

FIG. 7 is a diagram showing a supervisory signal superimposing circuit according to the first embodiment.

FIG. 8 is a diagram showing an attenuation amount characteristic of a band elimination filter.

FIG. 9 is a diagram showing a supervisory signal superimposing circuit represented by an unbalanced bridge T-type band elimination filter.

FIG. 10 is a diagram showing a change in impedance when a band elimination filter is inserted.

FIG. 11 is a diagram showing a supervisory signal separation circuit according to a second embodiment.

[Explanation of symbols]

 1 supervisory signal sending device 2 line supervisory device 3 supervisory signal superposing circuit 4 supervisory signal generating circuit 5 supervisory signal separating circuit 6 supervisory signal measuring circuit 7 supervisory alarm circuit 8 analog telephone terminal 9 switch 10 subscriber line 11 low-pass filter 12 high Band pass filter 13 Speech band signal 14 Supervisory signal 15 Speech signal band 16 Supervisory signal frequency 17 Line impedance characteristic 18 Impedance when demultiplexing circuit is inserted 19 Transmission line 20 Reception line 21 Hybrid circuit 22 Balanced connection network 23 Echo loss 24 Band rejection filter 25 Attenuation characteristics of band stop filter 26 Impedance characteristics when band stop filter is inserted 27 Band pass filter

Claims (14)

[Scope of utility model registration request] 1. An out-of-band signal separation circuit for separating out-of-band signals transmitted outside the voice band of an analog telephone subscriber line, wherein impedance between terminals connected to said subscriber line is characteristic of that subscriber line. An out-of-band signal separation circuit comprising a bridge T-type filter that approximates impedance. 2. The out-of-band signal separation circuit according to claim 1, wherein the impedance between the terminals of the bridge T-type filter is about 600Ω. 3. The bridge T-type filter is a band-stop type filter inserted between the subscriber line and the exchange to include the frequency of the out-of-band signal in its stop frequency band.
Alternatively, the out-of-band signal separation circuit described in 2. 4. The out-of-band signal separation circuit according to claim 3, wherein a circuit for passing the out-of-band signal is connected to a subscriber line side terminal of the bridge T-type filter. 5. The out-of-band signal separation circuit according to claim 1, wherein the bridge T-type filter is a balanced pair type. 6. The out-of-band signal separation circuit according to claim 1, wherein the bridge T-type filter is an unbalanced type. 7. In an out-of-band signal superimposing circuit for superimposing an out-of-band signal transmitted outside the voice band of an analog telephone subscriber line, the impedance between terminals connected to said subscriber line is characteristic of that subscriber line. An out-of-band signal superimposing circuit comprising a bridge T-type filter approximating impedance. 8. The out-of-band signal superimposing circuit according to claim 1, wherein an impedance between the terminals of the bridge T-type filter is about 600Ω. 9. The bridge T-type filter is a band stop type filter inserted between the subscriber line and the terminal to include a frequency of the out-of-band signal in a stop frequency band thereof.
Alternatively, the out-of-band signal superimposing circuit according to item 8. 10. The out-of-band signal superimposing circuit according to claim 9, wherein a circuit for passing the out-of-band signal is connected to a subscriber line side terminal of the bridge T-type filter. 11. The out-of-band signal superimposing circuit according to claim 7, wherein the bridge T-type filter is a balanced pair type. 12. The out-of-band signal superimposing circuit according to claim 7, wherein the bridge T-type filter is an unbalanced type. 13. A subscriber switching apparatus comprising the out-of-band signal separation circuit according to claim 1. Description: 14. A subscriber terminal device comprising the out-of-band signal superimposing circuit according to claim 7. Description: