JP2005101801A - Telephone terminal device and its setting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a telephone terminal device which obtains impedance matching without any special operation, and to provide a method for setting the telephone terminal device. <P>SOLUTION: The telephone terminal device includes a call connecting circuit and a hybrid circuit connected to a telephone line through the call connecting circuit. The method for setting the telephone terminal device includes a step of detecting an amplitude of a direct current flowing to a direct current route when the call connecting circuit performs a calling operation or an incoming call response to form the direct current route between the telephone lines, and a step of updating the impedance of the hybrid circuit in response to the magnitude of a loop current. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a telephone terminal device connected to a telephone network line and a setting method thereof.

  As a telephone terminal device, for example, a telephone terminal device such as a VoIP gateway device of a type connected to a general public telephone line is usually provided with a so-called CO circuit for controlling an incoming call response of the terminal to the exchange. In this case, it is necessary to achieve impedance matching between the CO circuit and a telephone line, that is, a line. This is because the crosstalk prevention function by the hybrid circuit does not fully function unless such impedance matching is performed. Furthermore, it is necessary to prevent the signal waveform from being disturbed by the reflection of the signal.

  In general, the distance between the telephone terminal device and the station building is not constant, and the length varies depending on the location of the telephone terminal device, and the length of the line connecting the two is also assumed to be various. Must. Since the direct current resistance value of the transmission line formed by the line depends on the length of the line, special consideration is required for the distance between the telephone terminal device and the office building.

  Therefore, in the conventional impedance matching method in the telephone terminal device, there are two states (a case where the distance to the station is long and a case where the distance is shorter than this) (hereinafter, the former is the far end and the latter is the near end. Impedance matching was performed assuming that For example, a type having either a far-end or near-end setting circuit, or both a far-end and near-end setting circuit, and an impedance of the hybrid transformer according to an external operation such as a dip switch operation. There is a type of telephone terminal device to be switched (see (A) and (B) of FIG. 1).

  However, according to the method described above, it is necessary for the apparatus builder to change the apparatus to an appropriate one or to change the setting manually according to the actual distance to the station.

  An object of the present invention is to provide a telephone terminal device and a telephone terminal setting method for realizing impedance matching without any special operation.

  A telephone terminal apparatus according to the present invention is a telephone terminal apparatus including a call connection circuit and a hybrid circuit to be connected to a telephone line via the call connection circuit, and the call connection circuit makes a call operation or a call through the telephone line. A loop current detecting circuit for detecting a magnitude of a DC current flowing in the DC current path when a DC current path is formed between the telephone lines in response, and the hybrid circuit has an impedance of the loop current. It is characterized by changing according to the size.

  A telephone terminal device setting method according to the present invention is a telephone terminal device setting method for setting a telephone terminal device including a call connection circuit and a hybrid circuit to be connected to a telephone line via the call connection circuit, and the call connection circuit is connected to the telephone. A loop current detection step for detecting the magnitude of the DC current flowing in the DC current path when a DC current path is formed between the telephone lines by calling operation or answering the call via the line; And a changing step of changing the impedance of the hybrid circuit in accordance with the size.

  According to the telephone terminal device and the telephone terminal device setting method of the present invention, a loop current detecting means or a process for determining, for example, either the far end or the near end based on the loop current flowing through the line is provided. In accordance with the signal of the determination result, the impedance setting of the hybrid circuit is changed. Thereby, impedance matching is realized without any special operation.

  Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 2 is a first embodiment of the present invention and shows the overall configuration including a telephone terminal device. A telephone terminal device 20 is connected to the telephone exchange 12 of the station 11 via the polar line 10. The telephone terminal device 20 may be a telephone that makes a normal telephone call, a private branch exchange for a private telephone, an IP telephone terminal, or an IP telephone exchange. The right end of the line 10 is connected to the telephone exchange 12 of the office building 11 to transmit and receive control signals and telephone voice signals for call connection with the telephone terminal device 20. One line at the left end of the line 10 is directly connected to the call connection circuit 26 of the telephone terminal device 20, and the other line is connected to the call connection circuit 26 through the distance determination circuit 30. The line 10 is connected to the hybrid circuit 21 via the call connection circuit 26. The call connection circuit 26 and the hybrid circuit 21 constitute a so-called CO circuit.

  The call connection circuit 26 of the telephone terminal device 20 has a function of performing a series of call connection operations including an outgoing call operation and an incoming call response. The call connection circuit 26 also has a function of outputting a busy signal to the distance determination circuit 30. The call signal is a signal indicating that the call connection is in a call, and the state thereof is, for example, an OFF signal during a call operation or an incoming call response sequence, and an ON signal when in a call sequence.

  The hybrid circuit 21 of the telephone terminal device 20 includes a hybrid transformer for impedance matching with the line 10, and a far-end setting circuit 23 and a near-end setting circuit 24 are selectively connected by a switching circuit 22. Thus, the output impedance is selectively switched. The switching circuit 22 operates in accordance with the far end / near end setting signal from the far and near discrimination circuit 30, and when the far end / near end setting signal has a value indicating the far end (for example, an OFF signal), the switching circuit 22 and the far end When the far end / near end setting signal has a value indicating the near end (for example, an ON signal), the hybrid circuit 21 and the near end setting circuit 24 are connected. Each of the far-end setting circuit 23 and the near-end setting circuit 24 is supplied with a reference signal Vref for supplying a reference voltage of the setting circuit. The hybrid circuit 21, the far-end setting circuit 23, the near-end setting circuit 24, and the switching circuit 22 may be realized by a single component module and further by a component module including the call connection circuit 26. good.

  Each of the transmission signal and the reception signal output from the hybrid circuit 21 is connected to the call circuit 25. The call circuit 25 is further connected to an acoustic device (not shown) such as a microphone and a speaker to realize a function as a telephone terminal. The telephone terminal device 20 may be an IP network device such as a VoIP gateway for IP telephones. In this case, the call circuit 25 is connected to circuits such as a packet transmission / reception circuit and a voice codec circuit, for example. Thus, the function as a VoIP terminal may be realized.

  FIG. 3 shows a more detailed configuration of the perspective discrimination circuit 30 shown in FIG. The perspective determination circuit 30 is connected in series to one of the two lines of the line 10. One end of the line 10 (on the right side in FIG. 3) is connected to the station 11 (see FIG. 2), and the other end is connected to the hybrid circuit 21 of the telephone terminal device 20. The perspective determination circuit 30 includes a current detection circuit 31, a hysteresis circuit 32, a first comparator circuit 33, and a second comparator circuit 34. In the line 10, a loop current flows (for example, 15 to 130 mA) in response to an off-hook operation (or an equivalent operation) of the telephone terminal device 20. The loop current is driven by a station-supplied DC voltage from the station. The station-supplied DC voltage is inverted in the range of, for example, −48V to 48V according to the incoming call response. However, when the call connection reaches the call sequence, a stable DC voltage of about 5V is supplied. As a result, an annular direct current path is formed through the line 10 and passing through the telephone terminal device 20 and the exchange 12 of the office building 11 to generate a loop current. The perspective determination circuit 30 provides loop current detection means.

  The current detection circuit 31 of the perspective determination circuit 30 measures the magnitude of the loop current of the line 10 by using a current detection element such as a photocoupler connected in series with one line of the line 10 and indicates the magnitude of the loop current. Is output. The voltage signal is input to each of the first comparator circuit 33 and the second comparator circuit 34. Each of the first comparator circuit 33 and the second comparator circuit 34 includes a voltage signal indicating the magnitude of the input loop current, and a voltage indicating the magnitude of the threshold current (A) and threshold current (B) that are set and input. Each signal is compared and an ON / OFF signal is output. The ON / OFF signal of the first comparator circuit 33 is switched by outputting an ON signal when the voltage signal indicating the magnitude of the loop current is equal to or exceeding the voltage signal of the threshold current (A), and in other cases Outputs an OFF signal. Similarly, the ON / OFF switching of the second comparator circuit 34 outputs an ON signal when the voltage signal indicating the magnitude of the loop current is equal to or exceeds the voltage signal of the threshold current (B). In this case, an OFF signal is output.

  The hysteresis circuit 35 of the perspective discrimination circuit 30 inputs a plurality of ON / OFF signals from each of the first comparator circuit 33 and the second comparator circuit 34, and instructs the switching of the near end or the far end. A discrimination signal is output. The far end / near end discrimination signal is enabled by a call signal from the call connection circuit 26. This ensures that the loop current is measured correctly only when in a call sequence. The hysteresis circuit 35 also holds the previous signal value of the far-end / near-end discrimination signal, thereby using the difference between the two threshold currents (A) and (B) as a hysteresis, that is, a hysteresis, as the far-end / near-end. An edge discrimination signal is output. Unlike the method of switching the far end / near end with a threshold value as a single point, this hysteresis operation prevents the far end or near end setting instability that occurs when the current value fluctuates around one threshold value. Is possible. The hysteresis operation can also be realized by an existing operational amplifier that enables a hysteresis input.

  FIG. 4 shows the change of the loop current with respect to the distance from the station. As can be seen from this figure, the DC resistance of the line increases and the loop current decreases as the distance from the station increases. Therefore, the determination of the far end or the near end can be performed by setting an appropriate threshold value for each of the far end / near end and determining the far end or the near end according to the distance from the station. The threshold current value can be set empirically. For example, the near end in the distance to the central office is within a distance range that gives a round trip line loss of 0 to 2 dB, while the far end is a distance range that gives a round trip line loss of 2 dB or more. Accordingly, the threshold currents at the far end and the near end are set to the value of the loop current due to the attenuation of −2 dB.

  FIG. 5 is a chart showing temporal voltage changes of main signals of the perspective discrimination circuit 30. The horizontal axis shows the passage of time, the vertical axis shows the busy signal, the loop current, the output signal of the first comparator circuit, the output signal of the second comparator circuit, and the far end / near end discrimination signal at the bottom. ing.

  The on-call signal is maintained as an ON signal when the telephone terminal device 20 and the exchange 12 are in a call sequence. The proper loop current can be measured because it is in the call sequence. Further, the hysteresis circuit 36 is enabled by the ON signal of the busy signal. For the sake of explanation, the loop current indicates a change when the impedance is connected to a virtual line whose time changes. Looking at the change in the loop current shown in FIG. 5, the threshold current (A) and the threshold current (B) are interrupted gradually and interrupted, and then the threshold current (B) and the threshold current (A) are sequentially exceeded. The case of changing is shown.

  In response to the change in the loop current, the output signal of the first comparator circuit outputs an ON signal when the loop current exceeds the threshold current (A). On the other hand, the output signal of the second comparator circuit outputs an ON signal when the loop current exceeds the threshold current (B). The far-end / near-end discrimination signal is a signal indicating that the near end, that is, the station is at a short distance for the terminal (for example, an ON signal), and the far end, that is, the station is at a farther distance than the near end for the terminal. Two states of a signal indicating this (for example, an OFF signal) can be taken. As shown in the drawing, the far end / near end discrimination signal is hysteresis-operated by the hysteresis circuit 35 of the perspective discrimination circuit 30. As a result, the instability of the far end / near end setting due to a minute change in the loop current around one threshold is eliminated.

  In the above embodiment, the description has been made assuming that a normal telephone is used as the telephone terminal device. However, the telephone terminal device according to the present invention is not limited to such a telephone, but is an IP network device such as a VoIP gateway for IP telephones. There may be. 2 is built in the telephone terminal device. However, the perspective determination circuit according to the present invention is not limited to such a built-in configuration, and is a separate and independent device from the telephone terminal device. It is also possible to configure. Furthermore, the perspective determination circuit of the present embodiment performs the determination on the premise of two distance ranges of the far end and the near end, or is not limited to this number, and can also determine a plurality of distance ranges.

It is explanatory drawing explaining the method of aiming at impedance matching in a prior art. It is an Example of this invention and is a block diagram which shows the whole structure containing a telephone terminal device. FIG. 2 is a circuit diagram showing a more detailed configuration of a perspective determination circuit of the telephone terminal device shown in FIG. 1. It is explanatory drawing explaining the change of the loop electric current with respect to the distance from a station building. It is a chart which shows the temporal voltage change of the main signal of a perspective discrimination circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Line 11 Station 12 Switch 20 Telephone terminal device 21 Hybrid circuit 22 Switching circuit 23 Far end setting circuit 24 Near end setting circuit 25 Calling circuit 26 Call connection circuit 30 Far / near discrimination circuit 31 Current detection circuit 32 Hysteresis circuit 33 First comparator circuit 34 Second comparator circuit

Claims (8)

A telephone terminal device including a call connection circuit and a hybrid circuit to be connected to a telephone line via the call connection circuit,
Loop current detection for detecting the magnitude of the DC current flowing in the DC current path when the call connection circuit forms a DC current path between the telephone lines by making a call operation or answering the call via the telephone line A circuit,
The telephone terminal apparatus, wherein the hybrid circuit changes its impedance according to the magnitude of the loop current. The loop current detection circuit compares the magnitude of the loop current with at least one predetermined threshold value, and outputs a determination signal when they match or any one exceeds the other, and the hybrid circuit detects the determination 2. The telephone terminal device according to claim 1, wherein the impedance is changed according to a signal. 3. The telephone terminal apparatus according to claim 2, wherein the predetermined threshold value is a value corresponding to a loop current in which a round-trip DC loss in the telephone line is set to -2 dB. 4. The telephone terminal apparatus according to claim 2, wherein the predetermined threshold includes two thresholds, and a difference between the two thresholds is a hysteresis. A telephone terminal device setting method for setting a telephone terminal device including a call connection circuit and a hybrid circuit to be connected to a telephone line via the call connection circuit,
Loop current detection for detecting the magnitude of the DC current flowing in the DC current path when the call connection circuit forms a DC current path between the telephone lines by making a call operation or answering the call via the telephone line Steps,
A changing step of changing the impedance of the hybrid circuit according to the magnitude of the loop current;
A telephone terminal device setting method comprising: The loop current detection step compares the magnitude of the loop current with at least one predetermined threshold value, and outputs a determination signal when they match or any one exceeds the other, and the change step includes the determination 6. The telephone terminal device setting method according to claim 5, wherein the impedance is changed according to a signal. 7. The telephone terminal apparatus setting method according to claim 6, wherein the predetermined threshold value is a value corresponding to a loop current in which a round-trip DC loss in the telephone line is set to -2 dB. 8. The telephone terminal device setting method according to claim 6, wherein the predetermined threshold includes two thresholds, and a difference between the two thresholds is a hysteresis.

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